GREATER BOISE'S CARRYING CAPACITY: WATER RESOURCES

FINAL DRAFT: FOR REVIEW AND REVISION
NOT FOR DISSEMINATION
GREATER BOISE 1S CARRYING CAPACITY:
WATER RESOURCES
A Summary Report from the Technical
Assessment Committee to the Boise Future
Foundation
Richard Mabbutt, Project Coordinator
Douglas Burr, Research Associate
Foundation Report #2
Boise, Idaho
September, 1982
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Foreward and Acknowledgement
The Boise Future Foundation, a private, non-profit educational
organization, is composed of representatives from civic organizations,
private sector corporations and business firms, and representatives
of state, county and local governmental agencies. The purpose of
the Foundation is to sponsor research into the 11Carrying capacity11
of the Boise area and the alternatives for managing growth and main­taining
desired qualities of life.
For that purpose, the Foundation has created a technical assess­ment
committee composed of technical experts and knowledgeable citizens
drawn from private and public sector organizations to consider the
concept of carrying capacity and its application to the specific
circumstances of the greater Boise area. This process focuses on a way
of seeing relationships between people and their environment, a method of
asking questions and formulating approximate answers and suggestive
of approaches to managing solutions. The result is a short, summary
assessment of carrying capacity in a report designed for a general
audience of concerned citizens and policy-makers in the public and
private sector.
Members of the committee, and many others listed in the final
section, have provided much valuable information about local
resources and insight into carrying capacity estimation. Their
cooperation and assistance is gratefully acknowledged. Responsibility
for the final format and content remains with the authors. Exten­sive
production assistance was provided by faculty and staff, through
the University Research Center, Boise State University, and is deeply
appreciated.
i
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THE BOISE FUTURE FOUNDATION TRUSTEES
*Dale Blickenstaff
*James Bruce
*Dr. Maurice Burkholder
Chet Call
Ralph Comstock
Paul Corddry
Pat Derbidge
A. Dale Dunn
Dick Eardley
Jerry M. Conley for
John Evans
*John Fery
Deanne Kloepfer
Patty Glaisyer
Mike Goffin
Marilee Gross
Robert Hansberger
Bob Hendren
Fred Humphreys
Chuck Hummel
Larry Jackson
*John Keiser
* Indicates Members of Executive Committee
ii
Bob Krueger
Marcel Learned
Warren McCain
George McCown
Mike Shirley for
William McMurren
*Mary Mech
*Walter Minnick
Winston Moore
Velma Morrison
Chuck Newhouse
Peter 0 1Neill
Marie Schriner
*Gary Sherlock
Marilyn Shuler
Ray Smelek
Joe Terteling
*Eugene Thomas
Ron Twilegar
Brent Robinson
Tom Wright
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Members
Technical Assesment Committee
John White Chairman
Hewlett-Packard Co.
Bill Ancell
Department of Public Works
Sheldon Barker
CH2M Hill
Bob Walker
Boise Water Corporation
Jack Kelly
Anderson & Kelly
Terry Keyes
Division of Environment
State Dept. of H & W
Mark Masarik
U.S. Environmental Protection
Agency
iii
Leland (Roy) Mink
Morrison-Knudsen
Robert Minter
Ada Planning Association
Doli Obee
League of Women Voters
Alan Robertson
Idaho Department of Water
Resources
Patrick Schow, M.D.
Larry Wimer
Idaho Power Company
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Executive Summary
1. The study is based on a concept of carrying capacity which estimates
the varying populations which can be maintained indefinitely at selected
qualities-of-life levels in an area.
2. The analysis focuses on water resources - supply and quality - for
various uses in the greater Boise area and Ada County. The method used
measures current and estimates future supplies of and demands for water
at the qualities required for the intended uses.
3. The study concludes: a) groundwater supplies for urban consum' ption
appear plentiful; b) demand for irrigation water in the study area will
decline; and c) demand for water-based recreation will increase
significantly.
4. Some water quality experts state that the Boise River is at its capacity
to carry certain types of pollution loads. Possible alternatives to
alleviate the situation include: a) a decrease in the water quality
standards; b) an increase in the level of treatment for those who
discharge wastewater into the river; or c) an increase in the flow of the
river to allow for greater carrying capacity.
5. The capacity assessments of the three Boise wastewater treatment
facilities are as follows:
Lander Street: at capacity. Excess loads are to be diverted to the West
Boise Plant.
West Boise: at capacity due to unit process limitations. Funding to
alleviate these limitations is expected.
iv
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Gowen Field: under capacity at this time. This plant, however,
currently treats only a small amount of sewage and is not designed to
handle major increases in load.
6. Changes in federal funding programs will greatly increase the local cost
of wastewater treatment facility expansion or upgrading. Following
October 1, 1984, the federal government will no longer fund facilities to
allow for future population increases. All grants will provide only for
meeting current capacity needs.
v
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TABLE OF CONTENTS
Foreward and Acknowledgement . . i
Boise Future Foundation Trustees ii
Technical Assessment Committee Members iii
Executive Summary iv
Table of Contents vi
List of Figures and Tables . vii
Part I Introduction to Carrying Capacity 1
Part II Boise Area Water Resources: Supply and Demand 6
A. The Water Resource System . . 6
B. Present Water Resource Demand 11
c. Projected Water Resource Demand 14
D. Water Resource Supply and Carrying Capacity:
Summary Conclusions . . . . . . . . . . . 20
Part III Boise Area Water Quality: Managing Assimilative Capacity 22
A.
B.
c.
D.
Managing Water Quality: Water Use and the Effect on
Assimilative Capacity .
Current and Projected Loads on the Assimilative
Capacity of the Water Resource System . . .
Boise Area Water Quality Management System
Water Quality and Carrying Capacity: Summary
Conclusions . . . . . . . . .
Part IV Future Carrying Capacity Assessments: Issues
Part V Information Resources
vi
22
23
24
34
35
38
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List of Figures and Tables
Page
Figure 1 System Factors in Carrying Capacity Analysis . 3
Figure 2 Greater Boise Study Area . 5
Figure 3 Boise Area Water Resource System Model . 8
Figure 4A - 4B
Urban Water Consumption: Present and Future in Relation
to Estimated Carrying Capacity ............... 16-17
Table 1 Current Water Resource Demand, By Use Type, Quantities,
Qualities and Sources for the Boise Metropolitan Area . 12
Table 2 Comparison of Population Projections for Boise
Metropolitan Area . . . .
Table 3 Projected Water Resource Demand, By Use Type, Quantities,
Qualities and Sources for Boise Metropolitan Area:
. 15
1980 - 2000 . . . . . . . . . . . . . . . . . . . . . . . 19
Table 4 Major Water Pollutants and Their Effect on Water Quality . 24
Table 5 Water Quality Concerns in the Boise Metropolitan Area . 28
Table 6 Wastewater Facilities Construction Funding Sources . 31
Table 7 Sewer User Cost Impacts . 32
vii
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Part I Introduction To Carrying Capacity
A. Concept
The idea of carrying capacity was developed first by ecologists
to calculate the wildlife populations that could be sustained indef­initely
by the resources in a given area. The concept has been used
more recently in urban studies to estimate the relative populations and
activities that can be maintained within the constraints imposed by natural
resource limitations. Its earliest applications in management of
urban systems date from the late 1960's and early 1970's. There
still is no general agreement among theorists on the exact meaning
of the concept or the most effective methods of its application to
real communities.
Nevertheless, the concept of carrying capacity can be significant
for it requires citizens to study in an explicit manner the relation­ship
between people and their activities and environment and to develop
management policies and strategies for maintaining a harmonious and
supportive balance among these elements.
A. B. Bishop of Utah State University, a leader in this work,
defines carrying capacity as an estimate of the "level of human
activity, including population dynamics and economic activity, which
a region can sustain, including . . . . import and export of resources
and waste residuals, at acceptable 'quality-of-life' levels in
perpetuity." (#11, p. 32)
This definition suggests three elements or systems which must
be considered in carrying capacity studies. These are:
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(1) environmental systems -- air and watersheds,
land and plant and animal life;
(2) human activities -- the patterns of perceptions,
preferences and activities that make up the
human cultural, social, economic and political
systems; and
(3) the 11quality of life 11
-- a general term for the
well-being of people and the planet they inhabit.
The many complex relationships among these three factors mean that
carrying capacity is a complex, changing estimate rather than
a single, fixed number established as a population carrying
capacity. A number of environmental and human factors operate to
shape the carrying capacity of a region.
Bishop states:
11Attention, therefore, is directed toward viewing the
regional environment as a support system for numerous,
independent and frequently competing activities and
subsystems, where the determination of carrying capacity
rests upon desired human and environmental quality levels
which are circumscribed by a wide variety of political/
institutional, physical/biological, and social/cultural
constraints.
From this . . . . it should be clear that a human oriented
carrying capacity cannot be developed in a simple, single
numerical measure. It is not only a multidimensional con­cept,
but it is subject to constant change and modification
particularly as technological improvements are made and as
rules change due to pressures from the region 1 s residents.
From this perspective, carrying capacity must be inter­preted
~ ~ variable which is essentially socially deter­mined
within ~understanding of economic, social and
environmental values and their relative contribution in
maintaining quality-of-life levels. 11 (#11, pp. 30-33)
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The following diagram illustrates the relationship among these
elements.
Figure 1
System Factors in Carrying Capacity Analysis
ENVIRONMENTAL SYSTEM
a) Resources
1. fixed
2. renewable
b) Assimilative
capacity
QUALITY OF LIFE
a) Environmental
b) Human
B. Application
HUMAN SYSTEMS
cultural, social, political and economic
a) Reality descriptions - what 11 is11
b) Reality prescriptions - what 11 ought11 to be
c) Technological process - extraction,
production, distribution and disposal,
services and goods (tangible and intangible)
There is no single, agreed upon method for applying this concept
to studies of actual regions. However, a simplified approach, adapted
from H. Mogi, consists of six basic steps:
1. Identification of critical systems air, water, energy,
transportation, etc.;
2. Identification of geographic areas of critical systems;
3. Determination of limits of critical systems -- the resource
availability;
4. Determination of current and future resource utilization rates;
5. Determination of the margins, if any, for growth;
6. Identification of options and compromises involved in managing
the margins for growth. (#45, pp. 4-7)
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The present study will include the first f~ur steps and then
estimate future rates of population growth, resource demand and the
potential impacts for the study area. (See Figure 2} The emphasis
here is on assessing the current and potential future status of the
Boise urban system and the implications of such developments from a
carrying capacity perspective from the present to the year 2000.
In the course of the study, it is important to identify briefly
11 thresholds 11 or levels of effects which may be irreversible and may
alter carrying capacity or its utilization in fundamental ways, and
11 triggers 11 which are single events or a complex of events which push an
area•s carrying capacity or its utilization toward significant thresholds.
Finally, it is desirable for the purpose of the study, to identify
relationships between people and their environment so that citizens can
develop a personal connection to the complex issues of environmental and
human systems management. To this end, the study will suggest, where
appropriate and possible, the per capita demand on resource systems and
the per capita costs -- environmental and fiscal -- associated with
satisfying that demand.
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Figure 2
GREATER BOISE STUDY AREA
23.0l
West Bench.
Planning Ar
22.01
Southv1est
22.02
Source: (#67)
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7
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Part II Boise Water Resources: Supply and Demand
Introduction -- For the purpose of this study, the critical system
of focus is the water resource base for the greater Boise area from
the present to the year 2000. The geographic area is defined more
specifically as the Boise metropolitan area within Ada County. {See
Figure 2) While that area is the primary focus of the study, it is
acknowledged that it is part of a larger watershed system; therefore,
where appropriate, the study will examine upstream factors which can
affect the study area, as well as those downstream impacts resulting
from activities within the primary study area. In general, Ada County
is the secondary emphasis of the study.
In examining water resources as a base for local carrying
capacity, it is useful to identify at least two related aspects of
water as a resource. The first is water as a support system for a
variety of intended uses involving various levels of necessary or
preferred water qualities. The other is the assimilative capacity
of water resources, or their ability to receive degradable and non-degradable
wastes or residuals without environmental degradation.
Water resources vary in this ability and their support capabilities are
modified by assimilative capacity. These distinctions are maintained
in the following report and serve to focus attention on estimates of
water demand and supply, quantities and qualities and the relations
between these twin elements.
A. The Water Resource System
Boise area water resources are the result of a complex set of
relationships between local climate, geography and geology. Together
these factors affect rates and amounts of precipitation, evaporation
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and flows within the Boise River drainage and the underlying shallow
and deep aquifer systems. Water resource availability is further
affected by modifications for water storage in upstream reservoirs
and canal systems which provide flood control and irrigation,
respectively, in Ada and Canyon Counties. These canals and reservoirs
indirectly support the aquifer system through groundwater seepage. A
brief outline of the hydrologic cycle will better serve to illustrate
these relationships.
1. Precipitation, either as rain or snow.
2. Evaporation/transpiration (water use by plants}.
3. Surface flows from and along the Boise River.
4. Reservoir storage for subsequent irrigation and recreational
uses.
5. Discharge through the river system.
6. Recharge of the groundwater aquifer by various surface water
sources.
7. The aquifer system consists of both shallow and deep aquifers
which are interrelated. Pumpage from the shallow aquifer
provides some residential and agricultural irrigation supplies.
The deep aquifer is the source of almost all water consumed
for residential, commercial and industrial purposes in the
Boise area. (See Figure 3)
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Figure 3
BOISE AREA WATER RESOURCE SYSTEM MODEL
6
6
-8-
b
6
6
~ PRECIPITATIONf
/j
tEVAPORATION/TRANSPIRATIONt
b
6
b
6
jl ! 1 1 ! 1:1' I! I! 1
1
1\j
RESERVO I R--)o.EO I SE RIVER DRAINAGE SYSTEM--.. CANALS-· .. I RR I GAT I ON--)o.DRAI NAGE--.. RUN OFF
J SEEPAGE l 1 1 1
DEEP AQUIFER
Graphic: Ann Dazey
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The Boise area water resource may be described as consisting of two
interrelated systems; a surface water system and a ground water (or aquifer)
system:
a) Surface water supplies
The principal surface water supply in the study area is the Boise
River which drains approximately 2,700 square miles of terrain lying to
the north and east of Ada County. The Boise River system has been
extensively modified by the construction of three major dams (Anderson
Ranch, Arrowrock, and Lucky Peak) located upstream from the city of Boise.
These dams provide reservoir storage for flood control, irrigation,
hydroelectric power production, and serve as a major source of water­based
recreation for residents of Ada County (#53, p. 18). Together
with Lake Lowell, this reservoir system contains approximately
1,157,000 acre-feet of active water storage capacity and provides
approximately 20,530 acres of water surface area (#53, p. 18). (Each
acre-foot of water contains 325,850 gallons.)
Five miles upstream from the city of Boise, the Boise River
Diversion Dam provides an average annual diversion of some
900,000 acre-feet of water into the New York Canal. This water
is then delivered to irrigated croplands throughout Ada and
Canyon counties through a system of latterals and canals or is
stored at Lake Lowell Reservoir in Canyon County for later irriga­tion
use. More than one-half of all irrigation water applied to
crops is not consumed and eventually returns to the river or
recharges the aquifer system (#59, p. 188).
There are a number of intermittent creeks or streams in the
area which contribute to the Boise River. They include Stuart
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Gulch, Crane Gulch, Hulls Gulch, Cottonwood Creek and Warm Springs
Creek.
b) Groundwater supplies
The groundwater or 11 aquifer11 system is composed of two
separate, but interdependent, aquifers -- one deep and one
shallow. The deep aquifer is generally located at depths greater
than 300 feet. The major zones of recharge to the deep aquifer
are the Boise Front, the bed of the Boise River above Boise, and
unlined portions of major irrigation canals (most significantly the
New York Canal). Discharge from the aquifer occurs through its
use as a supply source by the city of Boise and its natural dis­charge
to the Snake River (#20, p. 33).
The shallow aquifer is a much more dispersed body of water
which occurs primarily as a result of the over-application of
irrigation water. Discharge occurs through pumpage for domestic
use, pumpage for land drainage, and natural discharges through
seeps and springs. The shallow aquifer eventually drains into
the Boise River (#20, p. 36). Studies suggest that there is
some infiltration of water from the shallow aquifer to the deep
(#20, p. 33; #43, p. 11). The extent or effect of this infil­tration
is presently not known. The primary concern in this area
is the quality of the water found in the shallow system and the
degree to which it is a potential health hazard. This aspect of
the water resource will be discussed later in this report.
Perhaps the most important aspect of the carrying capacity
of an area•s water resource is the ability of that resource to
support an ever increasing population. In Boise, virtually all of
the water used for domestic purposes is drawn from the ground
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-11-
water system. The carrying capacity of the aquifer system can
be estimated conservatively as the rate of recharge that occurs
on an annual basis. Studies of the aquifer indicate that the
recharge rate for the study area alone is approximately 76,000
acre feet annually or approximately 24.7 billion gallons per
year (#75}. Note that this figure is very conservative since
the water available in the aquifer system is much greater than the
portion of the aquifer represented by the study area. Readers
interested in a descriptive account of the complexities of Boise
area hydrology are referred to works in Section V (see especially:
#20 and #43).
B. Present Water Resource Demand
The demand for or consumption of water resources by citizens of the
study area may be classed in the following use categories: 1} environ­mental
support for natural wildlife systems; 2) aesthetic enjoyment;
3} recreation; 4} domestic and agricultural irrigation; and 5} urban
consumption, which consists of residential, commercial, industrial; and
6} energy development (e.g., hydropower and geothermal).
The current types of use, levels of demand, the water qualities
entailed, and the primary sources within the water resource system
are indicated in Table l. The water resource demand presented here
includes demand by Boise area residents on water resources outside the
primary study area, but within the secondary area of the Ada County.
Note that the demand figures range from rather precise to very general
estimates, and that detailed measures are not readily available for some
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Water Use Type
TABLE 1
Current Water Resource Demand, By Use Type,
Quantities, Qualities and Sources for Boise Metropolitan Area
Estimated Quantities Required
Qualities Required by
State Regulations
1. Environmental Support 17.6 Billion Gallons of
Storage (provides 150 csf,
October through March)
Protected for:*
Cold Water Biota
Trout Spawning
2. Aesthetic
3. Recreational**
a) Fishing
b) Swimming
c) Boating
4. Irrigation
5. Urban Consumption,
Which Includes:
a) Residential
b) Commercial
c) Industrial
6. Energy Development
a) Geothermal
b) Hydropower
Not Calculable
Quantities Demanded.
Currently Creates
Congestion in Use of
Available Supply
3.26 to 4.89 Billion
Gallons/Year (study
area)
9 Billion Gallons/Year
Geothermal Development
Currently Requires 2000 to
4000 Gallons/Minute.
Hydropower Generation
Incidental to Release of
Water for Other Uses.
General Use
All Recreational
Uses
Agricultural Use
Domestic Use
Not Calculable
* See: Idaho Water Quality Standards; Re: Designated Beneficial Uses.
Sources of Supply
Boise River
Reservoirs, Boise River
Reservoirs, Boise River
Reservoirs for Storage and
Diversion of Boise River
Through Irrigation Laterals
and Canals
Groundwater System
Reservoir Storage for
Controlled Release and
Geothermal Groundwater
** Includes demand on water resource generated by citizens of Boise Metropolitan Area, on water resources
outside the primary study area, but within Ada County.
Sources: (#14, #23, #53, #71, #73, #75, #78, #84)
..I. ..
N
I
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of the uses under consideration. Their inclusion is necessary for any
comprehensive understanding of general carrying capacity; future research
efforts can clarify and provide more accurate assessments as these become
essential for decision-making.
Water quality requirements vary according to the intended uses of the
water and standards are established where necessary by the Idaho Department
of Health and Welfare Board. Water quality standards are set to preserve
or attain specified levels of quality; the relationship between most water
uses and quality is relatively well known and standards are established
accordingly. Some of the most stringent requirements are set for
environmental integrity since that relationship in some cases is well
known and policy-makers tend to create standards that are deemed likely
to be effective in protecting -- proven or presumed -- delicate natural
balances. Standards for water that is to be used in residential
consumption are set within criteria designed to protect or enhance human
well-being. Accordingly, there may be pre-treatment of domestic water
supplies. Boise Water Corporation currently treats water prior to
domestic use by the addition of chlorine for disinfection.
Data supplied by Boise Water Corporation permit a rough calculation
of per capita demands for water for urban consumption purposes in the
Boise metropolitan area. The current figure is approximately 170 gallons
per day, per person which includes residential, commercial and industrial
uses. The conventional rule of thumb nationally for water-supply
planning is 150 gallons per person, per day, which assumes a consumption
rate of 100 gallons for residential uses and increases that rate by
another SO% to reflect commercial and light industrial demand
(#46, p. 34). This comparison suggests that demand for domestic water
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resources in the Boise area is somewhat above the national level.
This information is useful as a water supply planning tool for it can
serve as the basis for assumptions about further water demand and supply
system requirements.
Boise Water Corporation data show that their average residential
customer pays approximately $155.00 annually for domestic water (#74).
Conversion of this annual figure to a per capita measurement shows
that water costs are approximately $.16 per capita per day. The Boise
Water Corporation has applied to the Idaho Public Utilities Commission
for permission to increase its water rates by 17.9 percent, due primarily
to increased energy costs, which account for nearly 24 percent of the
firm•s total operating costs. The status of the proposed rate increase
is unknown at this time.
C. Projected Water Resource Demand
Estimates of future demand for area water resources depend essentially
on assumptions about population growth and patterns of water consumption
behavior. The population projections most widely used locally are from
the Ada Planning Association (1978) and the Idaho Population and Employment
Forecast (1978). These are reprinted in Table 2.
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APA (1978)
IPEF* (1978)
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Table 2
Comparison of Population Projections
for Boise Metropolitan Area
1985 1990 1995 2000
*The IPEF estimates population by counties only. Historically, 87 percent of
Ada County•s population lived within the Boise metropolitan area. To coincide
with many of the studies used to prepare this report, it is assumed that this
relationship still exists. These figures are derived accordingly.
Boise Water Corporation records have shown that as incomes have risen in
the area, the per capita use of water has also risen by a small percentage.
The company bases its future projections of urban water use on the assumption
that this trend will continue; it estimates that by the year 2,000 the per
capita consumption rate will be 204 gallons per day. Other local experts,
however, believe that the per capita consumption will remain near the present
figure of 170 gallons per day through the year 2,000.
It is possible to construct utilization curves which project the total
annual urban water consumption rate in relation to estimated carrying capacity
according to three alternative per capita, per day use rates. Each is used to
represent different patterns of use due to the price of water or the level of
conservation employed by water users. The ranges are: 1) Low, 150 gallons
per day; high cost, high conservation, 2) Medium, 170 gallons per day;
moderate cost, moderate conservation; 3) High, 200 gallons per day; low cost,
low efforts to conserve. These estimates appear in Figure 4A and B.
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26
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Figure 4A
URBAN WATER CONSUMPTION: PRESENT AND
FUTURE IN RELATION TO ESTIMATED CARRYING CAPACITY
(USING APA POPULATION PROJECTIONS)
HIGH CONSUMP110N MEDIUM CONSUMP110N LOW CONSUMP110N
200 GPO PER CAPITA 170 GPO PER CAPITA 150 GPO PER CAPITA
-~· ... 0· .
ANNUAL CONSUMP110N-BIWONS OF GAI.l.ONS
I I I
24
···~······························································································
\ CARRYING CAPACITY ESTIMATED AS ANNUAL
RECHARGE RATE FOR THE STUDY AREA
22
20
18
~
16
14 / -------· ----·-- . _....-- --· .... .;~--
12
~ --· .. --· .. . .
"" .. ·- -· .......... - ·t'".:,. •.•
10
8
1980
I
1985
I
1990
...._.--· --· --·
__ .. ,.. ... --·. .
CARRYING CAPACilY STUDY PERIOD-YEARS
NOTE: Current consumption rate = 170 gpd per capita.
_..
. .._ £:>.
l
1995
~
-·
___ ... --·-- ..... w. , . .
.~·. .- -- . --
2000
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26
-17-
Figure 4B
URBAN WATER CONSUMPTION: PRESENT AND
FUTURE IN RELATION TO ESTIMATED CARRYING CAPACITY
(USING IPEF POPULATION PROJECTIONS)
HIGH CONSUMPTION MEDIUM CONSUMPTION LOW CONSUMPTION
200 GPO PER CAPITA 170 GPO PER CAPITA 150 GPO PER CAPITA
-~· ·•.
ANNUAL CONSUMPTION-BilliONS OF GAU..ONS
I I I
24
···~······························································································
'\CARRYING CAPACITY ESTIMATED AS ANNUAL
RECHARGE RATE FOR THE STUDY AREA
22
20
18 /
/
~
.. /
./
./
...._./
16
14
~ ~ --· --· --·- --· _.A--· .. .. ·.:·
12
10
~:~:~---·
8
1980
~ ~- '{'::~ ,. ...
I
1985
.•..
I
1990
--· --· --·
"'.
CAARYING CAPACITY STUDY PERIOD-YEARS
NOTE: Current consumption rate = 170 gpd per capita.
_... ......
I
1995 2000
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-18-
Future demand of water resources for purposes other than urban consump­tion
are estimated in a general way; no detailed projections are available
for this report. It is suggested that local area demand for waterbased
outdoor recreation -- fishing, swimming and boating -- will nearly double
by the year 2,000 (#23, p. 91). Thus, the assumption appears reasonable
that demand for environment support, aesthetic and recreational uses of
water by Boise area residents will increase faster than population growth.
This level of demand will focus on water resources and their quality within
the primary study area, especially the Boise River and Greenbelt environs,
as well as water resources with the secondary study area of Ada County.
Decline in the number of irrigated farm acres within the study area,
and the county generally, will reduce the demand for surface water sources
for agricultural irrigation.
It is also possible that the next two decades will see increased
competition among various users for opportunities to use the surface
waters within the primary or secondary area of this study. Increased use
of surface waters -- especially Lucky Peak Reservoir and the Boise River
may be compatible, rather than competitive, in some instances. In most
cases, however, the uses will not be compatible. Increased consumer
dissatisfaction with quality of life levels or increases in participation
costs due to pollution or congestion and maintenance of water quality
standards may reduce general satisfaction with area water resources.
These possibilities are not estimated currently, but future study
could lead to more accurate projections.
Future estimates of demand on water resources, by use type, quantity,
quality and source are summarized in Table 3. Assumptions that water quality
requirements will remain at present levels, if not higher, are based on
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TABLE 3
Projected Water Resource Demand, By Use Type,
Quantities, Qualities and Sources for Boise Metropolitan Area
Water Use Type
Quantities Required
Estimated
1. Environmental Support 17.6 Billion Gallons of
Storage {provides 150 cfs,
October through March}
2. Aesthetic Not Calculable
3. Recreation** Demand Expected to Double
a) Fishing
b} Swimming
c) Boating
4. Irrigation Demand Expected to
Decrease Within Study
Area
Qualities Required
Estimated*
Continued Protection
for Cold Water Biota
Trout Spawning
General Use
All Recreational
Uses
Agricultural Use
5. Urban Consumption
a} Residential
12 to 16 Billion Gallons/Year Domestic Uses
b) Commercial
c) Industrial
6. Energy Development
a} Geothermal
b} Hydropower
by 2000.
a) Future Geothermal Development Not Calculable
Requirements Depend Upon the
Performance of the System.
Currently Under Construction.
b) Hydropower Generation in the
Future will be Incidental to
Release of Water for Other Uses.
* See: Idaho Water Quality Standards; Re: Designated Beneficial Uses.
Sources of Supply
Boise River
Reservoirs, Boise River
Reservoirs, Boise River
Reservoir Storage, Diversion
of Boise River
Groundwater System
Reservoir Storage.
Geothermal Groundwater.
** Includes water resource generated by citizens of Boise Metropolitan Area, on water resources outside the
primary study area, but within Ada County.
Sources: (#14, #23, #53, #71, #73, #75, #78, #84)
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national polls indicating that approximately 94% of the American people
favor retaining the Clean Water Act. The likely local increase in water­based
recreation will also tend to favor present or, perhaps, more stringent
quality standards.
It is necessary here to consider briefly the carrying capacity of the
system which provides and allocates our water resources. The elements of
that system include private organizations and public agencies responsible
for providing or maintaining the quantities of water resources, at required
qualities, that serve residents within greater Boise and Ada County.
In general, there are no detailed estimates of carrying capacities
made available by such agencies. Facilities projections done by Boise
Water Corporation indicate no general problem, technical or financial,
with providing quantities and qualities of water that may be required
during the study period. Spot difficulties with pumpage, leakage,
distribution, pressure or quality may occur infrequently but are expected
to be manageable. Costs will increase due to rising prices for electrical
energy; detailed cost projections are not available for this study. Further
studies into these aspects of carrying capacity may be warranted for all
water use types and the providers within the study area.
D. Water Resource Supply and Carrying Capacity: Summary Conclusions
From the carrying capacity methodology developed herein and estimates
of water supply and projections of current to future water demand, it is
possible to derive the following summary conclusions:
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1. Estimated water supplies for urban consumption -- residential,
commercial and industrial uses -- under alternative consumption
rates and growth scenarios are more than adequate to meet
demand during the next two decades.
2. Estimated water supplies for agricultural irrigation within the
study area are adequate through the year 2000. Demand for irrigation
will decline during this time due to growing urbanization in the
study area.
3. Demand on water resources for environmental aesthetic and recreational
purposes will increase due to population growth and high participation
rates:
4.
a. Available supplies may produce reduced material, or
psychic satisfaction due to congestion, pollution or costs
associated with maintaining present water quality standards.
b. Competition among users for surface waters, especially in
summer months, will increase.
a. Estimates of the carrying capacity of municipal water
provision system indicate no anticipated problems with
providing required quantities to consumers. Costs will be
higher.
b. Temporary and spot difficulties in pumpage, leakage,
pressure and quality are anticipated, but are considered
manageable by local water experts.
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-22-
Part III. Boise Area Water Quality: Managing Assimilative Capacity
A. Managing Water Quality: Water Use and the Effect on Assimilative
Capacity
The carrying capacity perspective on water quality is emphasized
in this statement from the Council on Environmental Quality:
11 Ideally, water quality would be measured in terms of its
impacts on all living systems, human and other. But
because measuring the functions of biological systems is
difficult, water quality is described by the extent to
which lakes, rivers and streams can physically, biologically
and chemically support aquatic life and meet the standards
recommended for human use.
Efforts to keep water clean or to restore it to a healthy
state center on controlling the amount and kinds of materials
that are dumped or washed into waterways, the ground and
the air. Water quality or rivers, lakes and oceans depends
upon their individual capacity to handle a given pollutant.
In turn, the capacity varies with the type and amount of
the pollutant; water temperature, flow, sediment and mineral
content.
Under Federal law, the Government is directed to •restore
and maintain the chemical, physical and biological integrity
of the Nation•s waters• -- to eliminate the discharge of
pollutants by 1985; to maintain water quality that protects
fish, shellfish and wildlife, and provides for recreational
use by 1983, and to prohibit the discharge of toxic sub­stances
in amounts that are toxic to humans and wildlife.
(#56, p. 237)
This focuses attention on the critical importance of 11 assimilative
capacity, 11 or the ability of water resource systems to handle various
types and quantities of pollutants without degradation of the environ-mental
system. Assimilative capacity varies with circumstances, and
the knowledge of ecologists about complex environmental relationships
involving water resources is inexact and incomplete. Thus, estimates
of carrying capacity may vary widely, depending on the assumptions
made and the knowledge available. In many cases, experts differ on
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whether assimilative capacity is relatively limited and fragile, or
whether it is extensive and rather resilient.
Since assimilative capacity is affected by the type and amounts
of pollutants and their effects on human and other life systems, it
is useful to survey the major water pollutants and their effects
on water quality. Table 4 summarizes these relationships.
B. Current and Projected Loads on the Assimilative Capacity of
the Boise Area Water Resource System
Because assimilative capacity is an estimation based on best available
knowledge, it is appropriate to use water quality standards as proxy measures
of carrying capacity. These standards for the study area are set by the Idaho
Department of Health and Welfare Board. For the purpose of this study, the
standards themselves are not as important as are estimates about meeting or
violating these standards in the present or the future. Accordingly, readers
interested in a detailed listing of water quality standards are referred to
Idaho Water Quality Standards and Wastewater Treatment Requirements (#29).
Precise estimates of current water qualities in the study area and
whether carrying capacity is met or exceeded, and if so, with what frequency
and magnitude, are difficult to make due to measurement, monitoring and
reporting practices. Projections from current to future situations are even
more difficult given measurement and impact assessment capabilities and the
choice of assumptions that may be most appropriate over the next several
decades. Nevertheless, general estimates are possible, based on current
measurement practices and the informed judgment of experts involved in water
quality management.
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Type of waste
Disease-carrying agents-­human
feces. warm-blooded
anrrnal feces
Oxygen-demanding wastes-­high
concentrations of
biodegradable organic matter
Suspended organic and
inorganic matenal
Inorganic materials.
mineral substances-­metal.
salts. acids.
solid matter. other
chemicals. oil
Synthetic organic chemicals-­dissolved
organic material.
e.g., detergents. household
aids, pesticrdes
Nutrients--nitrogen,
phosphorus
Radioactive materials
Heat
Source:
Table 4
MAJOR WATER POLLUTANTS AND THEIR EFFECT ON WATER QUALITY
(NOT ALL APPLY TO THE BOISE STUDY AREA)
Wastewater sources
Munictpal discharges.
watercraft ::iischaroes. urban
runoff. agncultural~ runoff.
feedlot wastes. combinPd
sewer overflows. industnat
discharges
Municrpal discharges.
industnal discharges.
combined sewer overflows.
watercraft discharges.
urban runoff. agricultural
runoff. feedlot wastes.
natural sources
Mining discharges. municipal
discharges. rndustrial
discharges. construction
runoff. agricultural runoff.
urban runoff. silvicultural
runoff. natural sources.
combrned sewer overflows
Mining drscharges. acid mine
drainage industrial
drscharges. municipal
discharges. combined sewer
overflows. urban runoff. oil
fields. agncultural runoff.
irrrgation return flow. natural
sources. coolrng tower
blowdown. transportation
spills. coal gasification
Industrial discharges. urban
runoff. municipal discharges.
combined sewer overflow.
agricultural runoff. silvicullural
runoff. transportation spills.
minrng drscharges
Municipal discharges,
agricultural runoff. combined
sewer overflows. industrial
discharges. urban runoff.
natural sources
Industrial discharges.
mining
Cooling water drscharges.
industnal drscharges.
rnunrcrnal drscharges.
cootinq tower blowdown
(#56, p. 239)
Water quality
measures
Fecal coliform. fecal
streptococcus. other
microbes
Effects on
water quality
Health hazard for
human consumption and
contact
Biochemical oxygen demand, Deoxygenation. potential !or
drssolved oxygen. volatile septic conditions
soltds, sulfides
Suspended solids. turbidity, Reduced light penetration.
biochemical oxygen demand. deposition on bottom.
sulfides benthic deoxygenation
pH, acidity, alkalinity,
dissolved solids. chlorides.
sulfates. sodium, specific
metals. toxicity bioassay,
visual (oil spills)
Cyanides, phenols. toxicity
bioassay
Nitrogen. phosphorus
Radioactivity
Temperature
Acidity, satination. toxicity
of heavy metals. floi!ling oils
Toxicity of natural organics.
biodegradable or persistent
synthetic organrcs
Increased algal growth.
dissolved oxygen reduction
Increased radioactivity
Increased temper<tture.
reduced capacrty to absorb
oxyg•m
Effects on
aquatic life
tnedibility of shellfish for
humans
Fish kills
Reduced photosynthesis.
changed bottom organism
population. reduced fish
production. reduced sport
fish population. increased
non-sport fish population
Reduced biological
productivity, reduced flow.
fish kills. reduced production,
tainted fish
Fish kills. tainted fish.
reduced reproduction.
skeletal development
Increased production,
reduced sport fish
popu!ation, increased
non-sport fish
population
Altered natural rate of
genetic mutation
Fish kills. altered species
composition
Effects on
recreation
Reduced contact recreation
If severe. eliminated
recreation ·
Reduced game fishing,
aesthetic appreciation
Reduced recreational use.
fishing. aesthetic appreciation
Reduced fishing. inedible fish
for humans
Tainted drinking water,
reduced fishing and
aesthetic appreciation
Reduced opportunities
Possible increased sport
fishing by extended season
lor fish whtch miqht otherwrse
miorale -
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The most recent survey of Boise area water quality notes: 11 the
quality of Boise Valley water resources ranges from generally good
to excellent. Surface water from the Eastern Uplands is of highest
quality, shallow groundwater and agricultural drain waters have the
poorest quality, and deep groundwater is of relatively intermediate
quality. 11 (#59, p. 194) That report states further:
11The water quality conditions of the Boise River and
its tributaries have been extensively studied since
the early 1970 1s. Sampling has included dissolved and
suspended constituents, bacteria and the biotic com­munities.
Sampling agencies have included:
o Ada Planning Association
o U.S. Bureau of Reclamation
o City of Boise
o Boise State University
o Idaho Department of Health and Welfare
o U.S. Army Corps of Engineers
o Idaho Department of Fish and Game
o U.S. Environmental Protection Agency
o U.S. Fish and Wildlife Service
Water quality conditions are governed by various
point source discharges, by agricultural return flows
and by river flow available to dilute pollutant loads.
During the winter non-irrigation season, flow in the
river below Lucky Peak is often insufficient to provide
adequate dilution of wastes discharged in the river.
In the irrigation season, diversion of flow for agricul­tural
usage may create low flow conditions in the
vicinity of Star. Below Star, flows again increase
due to agricultural return flows.
Generally, the water quality of the Boise River
worsens downstream of Boise. This degradation is due to
the various point and nonpoint source pollutant loads
entering the river. Several industrial discharges, in
addition to the municipal waste load, add significant
pollutant loads. Agricultural drains also account for
a portion of the total pollutant load in the river.
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-26-
Temperature. The temperature of the Boise River in­creases
in downstream direction and is especially
elevated during the summer months. An increase in
water temperature occurs between Caldwell and Parma
stations, which have average summer temperatures of
14.9°C and 17.4°C, respectively. The flows in this
reach are governed by agricultural return flows.
Dissolved Oxygen. Adequate levels of dissolved
oxygen are necessary for the survival of fish and
other aquatic organisms. STORET (EPA computerized
data base) data show that dissolved oxygen concen­trations
in the Boise River decrease in a down­stream
direction during the summer months. During
the winter, the average dissolved oxygen is relatively
stable, with only a slight decrease downstream. The
agricultural drains usually have lower dissolved
oxygen concentrations than the Boise River.
Ada Council of Governments (ACOG 1975d) found dis­solved
oxygen concentrations to decrease in a down­stream
direction. The concentrations, however, were
determined to be within acceptable limits for the
beneficial uses along the river.
At Star, EPA (197la) found minimum percentage
dissolved oxygen saturation. Star is the point in
the river where flows are greatly reduced, often
approaching a no-flow condition.
Nutrients. The major nutrients used by algae and
other aquatic plants include various nitrogen and
phosphorus compounds. Nitrogen released in sewage
effluent is primarily in the form of organic
nitrogen or ammonia. Various bacteria decompose
the organic nitrogen to ammonia, while other bacteria
convert ammonia to nitrite and nitrate. Algae can
convert ammonia, nitrite or nitrate; the nitrate form,
however, is most readily used. While ammonia and
nitrite can serve as plant nutrients, these two
forms of nitrogen can also be toxic to fish.
Very little ammonia is found in the river above Boise.
Ammonia concentrations reach a maximum (0.43 mg/1 in
winter) at Glenwood Bridge. The increase is due to
wasteloads, especially treated municipal sewage,
entering at Boise. Below Boise, the river shows
improvement with the ammonia concentrations decreasing
downstream direction, with the highest concentrations
found at Parma. The large nitrate concentration
at Parma is due not only to upstream discharges of
ammonia, organic nitrogen and nitrite from waste­water
effluent, but also due to runoff from agri­cultural
lands.
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-27-
Total phosphate and orthophosphate increase in a down­stream
direction. Orthophosphate averages 0.01 mg/1
below Lucky Peak and 0.30 mg/1 at Star. The increase
is primarily in response to runoff from agricultural
acreage or accretions from groundwater recharge from
irrigation and treated sewage effluent.
Biochemical Oxygen Demand. Biochemical oxygen demand
(BOD} is an index of the oxygen-consuming organic sub­stances
in water. High BOD levels can deplete the
dissolved oxygen necessary for survival of sih and
other aquatic organisms. The BOD in the Boise River
does not show large increases over upstream concentra­tions
until the station at Parma. During summer
conditions, organic materials are readily oxidized.
Consequently, the effect of oxidizing BOD loads shows
up as lower oxygen concentrations rather than increased
BOD concentrations. In the winter, colder temperatures
inhibit the organisms that oxidize organiz material,
and BOD increases at the downstream stations."
(#59, pp. 194-200}
For more detailed discussion of current and future estimates
regarding pollutant loadings and water quality, the reader is
referred to the resource document cited, especially Chapters 10 and 11.
See Table 5 for a list of water quality concerns in the Boise Metropolitan
Area.
C. Boise Area Water Quality Management System
Water quality management focuses both on point (source} or non-point
(general source} pollution and the treatment of effluents,
both degradable and non-degradable. In general, pollutants from
point sources are treated prior to discharge, either to land or to
receiving bodies of water. Treatment involves methods of collecting,
filtering and cleansing -- using chemical, biological or mechanical
processes -- and then either concentration of toxic or non-degradable
effluents for later disposal or dilution of degradable effluents
for discharge within permissible limitations to receiving waters.
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Concern
1. Municipal Wastewater
Treatment Facilities
2. Individual On-Site
Sewage Disposal
Systems
3. Individual Industrial
Wastewater Generators
4. Urban Storm Runoff
5. Geothermal Effluents
Table 5
WATER QUALITY CONCERNS IN THE BOISE METROPOLITAN AREA
Pollution Parameter
Ammonia, Flouride
Chlorine, Heavy Metals
Biological Oxygen Demand (BOD)
Total Suspended Solids (TSS)
Bacteria
Nitrate
Coliform Bacteria
Heavy Metals
Heavy Metals, Oil-base
Pollutants, TSS
Flour ide
Thermal Pollution
Impact
Harmful to Aquatic
Life, Degradation of
Water Quality for Other
Uses
Adverse Health Affects
if Ingested
Harmful to Aquatic Life
Degradation of Water
Quality for Other Uses
As Above
As Above
Sources: (#4, #17, #59, #71, #82)
Water Source Affected
Boise River
Shallow Groundwater Aquifer
(possible adverse effects
to deep aquifer and Boise
River)
Boise River
Boise River
Boise River
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Non-point sources of pollution are primarily urban stormwater
runoff and other drainage waters and agricultural runoff and associated
sediments and chemical or biological pollutants. Nationally, non-point
sources typically account for over SO% of all pollutant loadings to
receiving waters and over 80% of all organic discharges after waste­water
treatment (#57, p. 133). While most areas, including the Boise
metropolitan region and Ada County, are aware of the necessity of
planning for and managing water quality regarding the non-point sources,
it remains difficult to achieve effective management in practice. The
Council on Environmental Quality notes that the "control of pollutants
discharged directly from industrial and municipal sources . . . into
waterways is progressing, but little progress has been made in the
kinds and amounts of materials that enter waterways from erosion,
urban runoff and many other general sources . 11 (#56, p. 237)
From a carrying capacity perspective, it would be most desirable
to know the current sources of non-point pollutants, types and
quantities and their impacts on the receiving water systems in the
Boise and Ada County area. While some studies exist (#21), they
are not comprehensive or detailed enough to provide the necessary
information. Local experts in water quality management agree that
urban stormwater is probably one of the most pressing issues in
water quality management in the study area, given the magnitude of
the problem, its impact and the inadequacy of present plans or
facilities to handle the situation and the financial costs of any
effective system for doing so (#2 #59, #66, #69, #71). Further studies
of the urban stormwater problem have been proposed, but funding is
currently unavailable.
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Much more is known about the nature of point (source) pollution
from industrial, commercial and residential uses of water and the
methods for managing water quality as a result. Management strategies
may be characterized as centralized wastewater collection, treatment
and disposal-discharge systems, or decentralized, on-site systems for
the treatment of wastewater.
In the primary study areas, this approach generally involves
centralized wastewater treatment facilities operated by the City
of Boise for the Boise and Garden City areas, smaller waste treat­ment
systems for several areas and septic tank systems for the
rural, non-sewered portions of the primary study area.
The City of Boise currently operates three wastewater treatment
plants: Lander Street, West Boise and Gowen Field. The Boise
Wastewater Facilities Plan (#17, Chapter II, pp. 12-13) describes the
loads and capacities as follows:
Lander Street: operating near capacity 1n terms of flow
and organic loads.
West Boise: currently overloaded during the summer months due
to large amounts of groundwater or stormwater (infiltration and
inflow, respectively) which leak into the sewer system.
Gowen Field: currently underloaded.
The study indicates further, that planned modifications and improve­ments
in the Boise wastewater treatment system, including pipelines and
interceptors, would increase capacity sufficiently to carry the loads
projected through the year 2000. These plans, however, are contingent
upon federal and state participation in the funding of wastewater facilities.
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Historically, the U.S. Environmental Protection Agency has provided
75% of the eligible capital costs for wastewater treatment facilities,
with the Idaho Department of Health and Welfare granting an additional
15%. The local entity was then required to provide only 10% of the
eligible costs. The State of Idaho has determined that total grant
assistance shall not exceed 75% of the total cost of the facility.
This raises the local share of construction costs to 25%. By October 1,
1984 (fiscal year 1985), the federal grant portion will drop to 55%,
obligating the local entity to provide 45% of construction costs.
These data are summarized in Table 6.
Funding Source
EPA
IDHW
Local Funds
Table 6
WASTEWATER FACILITIES CONSTRUCTION
FUNDING SOURCES
Historical Present to 9-30-84
75% 75%
15 0
10 25
100% 100%
After 10-1-84
55%
0*
45
100%
*The State has not yet determined if it will participate to bring the total
grant up to 75%, and thus decrease the local share from 45% to 25%.
Sources: (#17, #66)
As government at all levels currently trim their budgets, many projects
which are legally eligible under the laws and regulations are practically
eliminated from consideration by the lack of sufficient money to fund all
eligible projects. Therefore, a priority system has been established.
Projects which are not high on the priority list will require 100% local
funding without state or federal assistance. Consequently, the local
share of some projects, rather then increase from 10% to 25% to 45%
(Table 6), will actually increase from 10% to 100% local
funding as a result of declining governmental support.
Beginning October 1, 1984, the federal government will provide
wastewater facilities construction grants only for the purpose of providing
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for present needs. If local facilities are expanded to anticipate growth,
the funding will have to be obtained locally. This approach suggests
that in order to be eligible for federal grants, the facility must be
over capacity. Formerly, a wastewater treatment facility was designed
to provide for 20 years of projected need.
The City of Boise uses two methods to generate needed revenue. One
method is user charge, which is monthly fee to each user based on non-irrigation
water consumption. This fee is used to pay all operating costs
and to help fund plant replacement. The second method is a connection
fee which is a one-time charge paid when a new horne or business connects
to the system. This fee is used to finance facility expansion. As the
local share of such expansion begins to grow, it is anticipated that an
upward pressure on both fees can be expected. See Table 7.
1980 Average
Present Average
Table 7
SEWER USER COST IMPACTS
User Charge
$0.10/capita/day
(2.86/capita/rnonth)
$0.11/capita/day
(3.19/capita/rnonth)
Connection Fee
$165.00
$360.00*
*This connection fee was increased as a result of the State's decision to
drop their 15% participation. It does not reflect any decrease in Federal
participation. Boise Public Works officials state that a connection fee
increase to approximately $800 is justifiable given current policies but
is felt to be unacceptable at this time.
Sources: #17, #69
Non-sewered portions of the study area are serviced by community-type
or on-site wastewater treatment systems. Because these systems dispose of
wastes beneath the ground, there has been concern expressed for the protec-tion
of water quality within the aquifer. Recent studies of Southwest
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Boise have documented an upward trend in nitrate concentrations in local
wells, which suggests the potential for future groundwater contamination
(#4, Sec III, pp. 2-4, #6, #59, p. 178).
On August 1, 1980, the Ada County Commissioners adopted the Southwest
Community Comprehensive Plan which limited new development in the area to
a maximum density of one dwelling unit per five acres. This plan acknow­ledged
the potential for groundwater contamination but chose to limit
population density rather than to incur the costs of extending central
sewer service from Boise or providing new central treatment facilities
for the area. The feeling of most area experts is that the adoption of
this land-use plan has essentially closed off the possibility of providing
centralized sewer service to Southwest Boise in the near future.
In the opinion of area water quality experts, the Boise River is at
its capacity to assimilate certain pollutants. These pollutants are
ammonia, flouride and some heavy metals. The loading from the various
point and non-point sources of pollution combined with the extreme
variability in river flow has placed a great deal of pressure on the
river 1 s carrying capacity, according to the current water quality standards.
In winter months, the river 1s carrying capacity is greatly diminished
by the extreme low-flow conditions which limit its capacity to assimilate
pollutant loads. The Idaho Water Quality Standards are designed to protect
the designated uses of the river under these low-flow conditions. During
the irrigation season, there is ample flow which allows the river to
assimilate loading, but under low-flow conditions, the Boise wastewater
treatment plants are required to increase their level of treatment to
protect water quality. This increased treatment raises the costs of
treatment by approximately 5% on an annual basis (#69).
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If the Boise River is at capacity, the community faces three
basic alternatives:
1. Decrease the water quality standards and thus increase
the river's "defined" carrying capacity. This alternative
has the potential to degrade the water for the designated
uses and may adversely affect the quality of life of citizens
in and around the study area. Further, this alternative would
be subject to review by the Environmental Protection Agency,
which has the authority to refuse such an action and to set
standards that it deems appropriate and necessary to protect
or enhance water quality.
2. Increase levels of treatment for those who discharge wastewater.
This alternative would increase costs of treatment and thus raise
costs to users of the system.
3. Increase the flow of water in the Boise River during the low-flow,
winter months. There is at present approximately 116,000 acre
feet of unallocated storage space at Lucky Peak Reservoir. This
space could be filled and partially used to augment river flow and
thus increase the carrying capacity of the river. This alternative
is under investigation by the Bureau of Reclamation (#70}.
D. Water Quality and Carrying Capacity: Summary Conclusions
1. In the opinion of area water quality experts, the Boise River
is at carrying capacity for certain pollutants according to
present water quality standards. Possible alternatives include:
a. Decrease the present water quality standards.
b. Increase levels of wastewater treatment.
c. Increase Boise River flows.
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2. The capacity of the Boise wastewater treatment plants is as
follows:
Lander Street: at capacity. No plans to expand the current
facility. Excess loads are to be diverted to the West Boise Plant.
West Boise: at capacity, due to present unit process limitations.
This facility is planned to accept the major loads expected from
future population increases. The funding for upgrading or expand­ing
this facility is expected but has not yet been formally awarded.
Gowen Field: under capacity at this time. This plant disposes
of treated wastewater on land areas and is not a threat to water
quality at this time. Further, this plant treats a very small
percentage of the area sewage and is not designed to accept major
increases in load.
3. The federal government has adopted policies which will reduce
its share of local wastewater treatment facilities construction
and expansion costs. Further, after October 1, 1984, the federal
government will no longer fund the expansion of facilities to
meet future needs. These steps greatly increase the costs of
facilities that must be borne locally and will raise costs
for users of centralized sewer systems to better reflect the
actual costs of building and maintaining such facilities.
Part IV. Future Carrying Capacity Assessments: Issues
A. Assumptions and Trends
As noted earlier, carrying capacity assessment is an on-going process
that leads to changing estimates of resource supply, demand and costs -­environmental
and financial. Therefore, this section briefly examines
some of the issues arising for future carrying capacity studies or updates
of the present study.
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The first issue concerns whether or not present estimates of water
resource supplies are accurate and if projections of population growth
and consumption behavior are accurate. Events not now foreseen or
anticipated could trigger substantially altered population growth rates
or changes in consumer demand for all types of water uses.
These possibilities need to be recognized, and as early signals
of such occurrences are available, these may be used to revise carrying
capacity analysis. Similarly, as new information becomes available
on recent trends, these assumptions may be altered accordingly, and
will affect future such assessments.
B. Research Needs
The foregoing analysis has noted in numerous instances where
comprehensive, complete and accurate information necessary for a
thorough carrying capacity assessment is not available. This may stem
from gaps in our theoretical understanding of complex relationships
among environmental and human systems. Other lacks may arise from gaps
in our applied knowledge of specific situations within the study area.
An additional possibility is that much available information -- theoretical
and applied -- is not collected, assembled and reported in a manner that
makes it easily available for or applicable to carrying capacity assessments.
More information on the following issues would be especially
helpful to citizens and policy-makers in the study area:
Updated population projections as 1980 census data become
available.
-- Expanded investigation of non-point sources of pollution to
determine the extent of their contribution to total pollution loads and
to develop management alternatives with which to control these sources
of pollution.
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-- Continued groundwater well monitoring, particularly in Southwest
Boise, to assess potential health hazards in domestic water supplies.
-- An assessment of the impact of declining federal assistance for
wastewater treatment plant construction and expansion and the extent to
which local sewer charges will increase as a result.
-- Survey and evaluate funding alternatives -- federal, state and
local -- for improvement and expansion of Boise area waste treatment
facilities and the per capita control costs for increments of improvement.
-- Survey the extent to which water quality is a component of the
"quality of life" for Boise area residents.
Carrying capacity studies focus attention on relationships between
people and their environment in ways generally not found in previous
studies. If policy-makers and citizens find the carrying capacity
perspective a useful one, it will become necessary to focus further
research efforts on obtaining the required information. Effective and
efficient methods of acquiring and maintaining it readily available
for guidance in community decision-making can be developed and managed
successfully. That information can assist the community in making
decisions based on greater awareness of the relationship between
environmental resources and human activities and the effects on the
area•s quality of life.
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Part V. Informational Resources
A. Printed Documents
1. Ada/Canyon Waste Treatment Management Committee. 1978.
Individual Waste Disposal Systems Management Plan. Ada
and Canyon Counties, Idaho.
2. Ada/Canyon Waste Treatment Management Committee. 1978.
Areawide Water Quality Management Plan for Ada and Canyon
Counties, Idaho.
3. Ada/Canyon Waste Treatment Management Committee. 1977.
Municipal Waste Treatment Plan. Ada and Canyon Counties,
Idaho.
4. Ada Planning Association. 1981. Ada County Domestic Wastewater
Management Plan. Boise, Idah~
5. Ada Planning Association. 1981. Southwest Community Wastewater
Management Plan. Boise, Idaho.
6. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study; Groundwater Report, Technical Memoranda 308.04g.
Boise, Idaho.
7. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study: Inventory and Evaluation of Public and
Private Central and Community Collection and Treatment
Systems. Technical Memoranda 308.04j. Boise, Idaho.
8. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study: Preliminary Alternatives -- Description
and Evaluation. Technical Memoranda 306.04j. Boise, Idaho.
9. Ada Planning Association. 1978. Demographic and Employment
Distribution to the year 2000. Boise, Idaho. 198 pp.
10. Berry, Brian and Frank E. Horton. 1974. Urban Environmental
Management. Prentice-Hall, Inc. Englewood Cliffs,
New Jersey.
11. Bishop, A. B. 1974. Carrying Capacity in Regional Environmental
Management. Utah State University. Logan, Utah. Prepared
for EPA.
12. Boise City. Metro Plan. Boise, Idaho.
13. Boise Project Board of Control. 1981. Annual Report. Boise,
Idaho.
14. Boise Water Corporation. 1980. Projection Study for Boise Water
Corporation. Boise, Idaho.
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15. Carey, George W. 1972. Urbanization, Water Pollution, and Public
Policy. Center for Urban Policy Research, Rutgers University.
16. Central District Health Department. 1979. Southwest Boise Water
Study. Boise, Idaho.
17. CH2M Hill, Inc. 1980. Boise Wastewater Facilities Plan: Summary.
18.
19.
Prepared for the City of Boise. Boise, Idaho.
CH2M Hill, Inc. 1980. Wastewater Facilities Plan, Boise, Idaho,
Parts I and II. Boise, Idaho.
Ehrlich, Paul R.
Environment.
California.
1977. Ecoscience: Population, Resources, and
W. H. Freeman and Company. San Francisco,
20. H. Esmaili and Associates, Inc. 1980. Groundwater Resources of
Boise Valley, Idaho: Preliminary Draft. Prepared for Jones
and Stokes Associates, Inc.
21. H. Esmaili and Associates, Inc. 1980. Non-point Source Waste
Loadings In Ada County and Southwest Community Study Areas:
22.
23.
Preliminary Draft. Prepared for Jones and Stokes Associates, Inc.
Feenburg, Daniel. 1980.
Pollution Abatement.
University.
Measuring the Benefits of Water
Department of Economics, Princeton
Ghazanfar, S. M. 1980. Idaho Statistical Abstract.
of Idaho. Moscow, Idaho.
University
24. Gibson, H. R. 1978. Survey of Fish Populations and Water Quality
in the Boise River From Its Mouth Upstream to Barber Dam.
Idaho Department of Fish and Game; Project No. F-63-R-4. 64 pp.
25. Godschalk, David R. 1977. Carrying Capacity in Growth Management:
A Reconnaissance. A report to the U.S. Department of Housing
and Urban Development.
26. Gravra, Sigurd. 1969. Urban Planning Aspects of Water Pollution
Control. Columbia University Press. New York, N. Y.
27. Hammer, Eliot R. 1977. Environmentali Policy: ~Sociological
Assessment of Abatement Alternatives. Pennsylvania State
University.--Gordon Press. New York, N. Y.
28. Herfindahl, Orris C. 1975. Quality of the Environment.
Resources for the Future, Inc. Johns Hopkins Press.
Baltimore, Maryland.
29. Idaho Code. Title 1, Chapter 2. Idaho Water Quality Standards
and Wastewater Treatment Requirements. Boise, Idaho.
30. Idaho Department of Health and Welfare. 1980. Idaho Vital
Statistics. Boise, Idaho.
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31. Idaho Department of Health and Welfare, Division of Environment.
1980. Boise River Study. Water Quality Summary No. 2.
Boise, Idaho.
32. Idaho Department of Health and Welfare, Division of Environment,
Water Quality Bureau. 1980. Idaho Water Quality Stat1·...,
Report. Boise, Idaho.
33. Idaho Department of Health and Welfare, Division of Environment,
Water Quality Bureau. 1980. Idaho Water Quality Management
Plan, (Idaho 208). Boise, Idaho.
34. Idaho Department of Health and Welfare, Division of Environment.
1979. Water Quality Related Effluent Limits Project. Statewide
208 Planning. Boise, Idaho.
35. Idaho Department of Water Resources. 1979. Water Markets and
Water Quality. Boise, Idaho.
36. Idaho Water Resources Board. 1976. The State Water Plan,
Part Two. Boise, Idaho.
37. J-U-B Engineers, Inc. 1981. Final Step 1 Wastewater Facility
Plan, Star Sewer and Water District. Nampa, Idaho.
38. Kneese, Allen V. 1972. Environmental Quality Analysis. Resources
for the Future, Inc. Johns Hopkins Press. Baltimore, Maryland.
39. Kneese, Allen V.
Publishers.
1972. Managing the Environment.
New York, N. Y.
Praeger
40. Kneese, Allen V. 1968. Managing Water Quality: Economics,
Technology, Institutions. Johns Hopkins Press. Baltimore,
Maryland.
41. Kneese, Allen V. 1968. Water Pollution: Economic Aspects and
Research Needs. Resources for the Future, Inc. Washington,
D. C.
42. Lewis, G. C., D. V. Naylor, J. R. Busch, and D. W. Fitzsimons.
1978. Groundwater Quality Study in the Boise Valley, 30 pp.
43. Mink, Leland L. and Michael LeBaron. 1976. Hydrology and Groundwater
Supply of the Boise Area.
44. Mink, L. L., A. F. Wallace, and M.G. Lucky. 1975. Study on the
Impact of Subsurface Sewage Disposal in the Ada/Canyon County
Area of Southwest Idaho. U.S. Army Corps of Engineers
Regional Water Management Study. 61 pp.
45. Mogi, H. M. 1978. Carrying Capacity Analytical Methodology
for Growth Management. Prepared for the Hawaii Office
of Environmental Quality Control.
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46. Nieswand, George H. and Peter J. Pizor. 1977. Current Carrying
Capacity: ~ Practical Carrying Capacity Approach to Land Use
Planning. Rutgers University.
47. Peskin, Henry M., editor. 1975. Cost Benefit Analysis and Water
Pollution Policy. The Urban Institute. Washington, D. 2.
48. Rich, Linvil A.
Engineering.
1973. Water Resources and Environmental
McGraw Hill. New Yor~N. Y.
49. Shanle, John I. 1975. Environmental Applications of General
Physics. Addison-Wesley Publishing Co. Reading,
Massachusetts.
50. Shuval, H. I., editor. 1969. Developments in Water Quality
Research. Ann Arbor Science Publishers, Inc. Ann Arbor,
Michigan.
51. Thomas, William A., editor. 1971. Indicators of Environmental
Quality. Oak Ridge National Laboratory. Plenum Press.
New York, N. Y.
52. U.S. Bureau of the Census. 1979. State and Metropolitan Area
Data Book. See pages 154-163. U.S. Government Printing
Office:--1980.
53. U.S. Bureau of Reclamation. 1981. Boise Project Power and
Modification Study: Idaho. Pacific Northwest Region.
Boise, Idaho. Progress Report.
54. U.S. Bureau of Reclamation. 1979. Boise Valley Shallow Groundwater
Study, First Year Review.
55. U.S. Bureau of Reclamation. 1977. Water Quality Study, Boise
Valley.
56. U.S. Council on Environmental Quality.
U.S. Government Printing Office.
1981. Environmental Trends
Washington, D. C.
57. U.S. Council on Environmental Quality. 1980. Environmental Quality.
58.
Annual Report. U. S. Government Printing Office. Washington,
D. C.
U.S. Environmental Protection Agency. 1981.
1981: Municipal Wastewater Treatment.
Administration. Washington, D. C.
Facilities Planning
General Services
59. U.S. Environmental Protection Agency. 1981. Final Environmental
Impact Statement: Wastewater Management for Boise, Eagle and
Ada County, Idaho. Region 10, Seattle, Washington.
60. U.S. Environmental Protection Agency. 1981. How to Obtain Federal
Grants to Build Municipal Wastewater Treatmen~Works. Second
Edition.
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61. U.S. Environmental Protection Agency. 1980. Resources and
Pollution Control. Office of Environmental Processes-and
Effects Research. Washington, D. C.
62. U.S. Environmental Protection Agency. 1979. The Use of Existing
and Modified Land Use Instruments to Achieve Environmental
QUality. washington, D. c.
63. U.S. Environmental Protection Agency. 1977. Clean Water Act,
December, 1977. (PL95-217). Washington,~.--------
64. U.S. Environmental Protection Agency. 1976. Quality Criteria
for Water. Washington, D. C.
65. Wilbur Smith and Associates, Inc. 1976. Demographic and Economic
Base Study, Ada County, Idaho. Los Angeles, California.
B. Personal Communications
66. Braun, Robert. Idaho Department of Health and Welfare, Division of
Environment. Boise, Idaho.
67. City of Boise. Planning Department. Boise, Idaho.
68. City of Nampa. Office of City Engineer. Nampa, Idaho.
69. Ellsworth, Carl. Department of Public Works. Boise, Idaho.
70. Golus, Ron. U.S. Bureau of Reclamation. Boise, Idaho.
71. Grey, Dennis. Idaho Department of Health and Welfare, Division of
Environment, Water Quality Bureau. Boise, Idaho.
72. Hampton, Loren. u.s. Bureau of Reclamation. Boise, Idaho.
73. Hanson, Phil. Boise Geothermal Supply, Inc. Boise, Idaho.
74. Heppler, Ben. Boise Water Corporation. Boise, Idaho.
75. Lindgren, John. Idaho Department of Water Resources. Boise, Idaho.
76. Linholm, Jerry. u.s. Geological Survey. Boise, Idaho.
77. Miller, Don. Idaho Public Utilities Commission. Boise, Idaho.
78. Pollard, Herb. Idaho Department of Fish and Game. Boise, Idaho.
79. Reid, Will. Idaho Department of Fish and Game. Boise, Idaho.
80. Reynolds, R. Larry. Department of Economics, Boise State University.
Boise, Idaho.
81. Schulte, Rose. Idaho Public Utilities Commission. Boise, Idaho.
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CS3D
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82. Sheppard, Craig. Idaho Department of Health and Welfare, Division
of Environment. Boise, Idaho.
83. South County Water Company. Boise, Idaho.
84. VanCuren, Royce. Boise Project Board of Control. Boise, Idaho.
Reproduced from the manuscript collections at Boise State University Library
MSS 042, Box 02, Folder 17
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Full-text

FINAL DRAFT: FOR REVIEW AND REVISION
NOT FOR DISSEMINATION
GREATER BOISE 1S CARRYING CAPACITY:
WATER RESOURCES
A Summary Report from the Technical
Assessment Committee to the Boise Future
Foundation
Richard Mabbutt, Project Coordinator
Douglas Burr, Research Associate
Foundation Report #2
Boise, Idaho
September, 1982
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Foreward and Acknowledgement
The Boise Future Foundation, a private, non-profit educational
organization, is composed of representatives from civic organizations,
private sector corporations and business firms, and representatives
of state, county and local governmental agencies. The purpose of
the Foundation is to sponsor research into the 11Carrying capacity11
of the Boise area and the alternatives for managing growth and main­taining
desired qualities of life.
For that purpose, the Foundation has created a technical assess­ment
committee composed of technical experts and knowledgeable citizens
drawn from private and public sector organizations to consider the
concept of carrying capacity and its application to the specific
circumstances of the greater Boise area. This process focuses on a way
of seeing relationships between people and their environment, a method of
asking questions and formulating approximate answers and suggestive
of approaches to managing solutions. The result is a short, summary
assessment of carrying capacity in a report designed for a general
audience of concerned citizens and policy-makers in the public and
private sector.
Members of the committee, and many others listed in the final
section, have provided much valuable information about local
resources and insight into carrying capacity estimation. Their
cooperation and assistance is gratefully acknowledged. Responsibility
for the final format and content remains with the authors. Exten­sive
production assistance was provided by faculty and staff, through
the University Research Center, Boise State University, and is deeply
appreciated.
i
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THE BOISE FUTURE FOUNDATION TRUSTEES
*Dale Blickenstaff
*James Bruce
*Dr. Maurice Burkholder
Chet Call
Ralph Comstock
Paul Corddry
Pat Derbidge
A. Dale Dunn
Dick Eardley
Jerry M. Conley for
John Evans
*John Fery
Deanne Kloepfer
Patty Glaisyer
Mike Goffin
Marilee Gross
Robert Hansberger
Bob Hendren
Fred Humphreys
Chuck Hummel
Larry Jackson
*John Keiser
* Indicates Members of Executive Committee
ii
Bob Krueger
Marcel Learned
Warren McCain
George McCown
Mike Shirley for
William McMurren
*Mary Mech
*Walter Minnick
Winston Moore
Velma Morrison
Chuck Newhouse
Peter 0 1Neill
Marie Schriner
*Gary Sherlock
Marilyn Shuler
Ray Smelek
Joe Terteling
*Eugene Thomas
Ron Twilegar
Brent Robinson
Tom Wright
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Members
Technical Assesment Committee
John White Chairman
Hewlett-Packard Co.
Bill Ancell
Department of Public Works
Sheldon Barker
CH2M Hill
Bob Walker
Boise Water Corporation
Jack Kelly
Anderson & Kelly
Terry Keyes
Division of Environment
State Dept. of H & W
Mark Masarik
U.S. Environmental Protection
Agency
iii
Leland (Roy) Mink
Morrison-Knudsen
Robert Minter
Ada Planning Association
Doli Obee
League of Women Voters
Alan Robertson
Idaho Department of Water
Resources
Patrick Schow, M.D.
Larry Wimer
Idaho Power Company
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Executive Summary
1. The study is based on a concept of carrying capacity which estimates
the varying populations which can be maintained indefinitely at selected
qualities-of-life levels in an area.
2. The analysis focuses on water resources - supply and quality - for
various uses in the greater Boise area and Ada County. The method used
measures current and estimates future supplies of and demands for water
at the qualities required for the intended uses.
3. The study concludes: a) groundwater supplies for urban consum' ption
appear plentiful; b) demand for irrigation water in the study area will
decline; and c) demand for water-based recreation will increase
significantly.
4. Some water quality experts state that the Boise River is at its capacity
to carry certain types of pollution loads. Possible alternatives to
alleviate the situation include: a) a decrease in the water quality
standards; b) an increase in the level of treatment for those who
discharge wastewater into the river; or c) an increase in the flow of the
river to allow for greater carrying capacity.
5. The capacity assessments of the three Boise wastewater treatment
facilities are as follows:
Lander Street: at capacity. Excess loads are to be diverted to the West
Boise Plant.
West Boise: at capacity due to unit process limitations. Funding to
alleviate these limitations is expected.
iv
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Gowen Field: under capacity at this time. This plant, however,
currently treats only a small amount of sewage and is not designed to
handle major increases in load.
6. Changes in federal funding programs will greatly increase the local cost
of wastewater treatment facility expansion or upgrading. Following
October 1, 1984, the federal government will no longer fund facilities to
allow for future population increases. All grants will provide only for
meeting current capacity needs.
v
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TABLE OF CONTENTS
Foreward and Acknowledgement . . i
Boise Future Foundation Trustees ii
Technical Assessment Committee Members iii
Executive Summary iv
Table of Contents vi
List of Figures and Tables . vii
Part I Introduction to Carrying Capacity 1
Part II Boise Area Water Resources: Supply and Demand 6
A. The Water Resource System . . 6
B. Present Water Resource Demand 11
c. Projected Water Resource Demand 14
D. Water Resource Supply and Carrying Capacity:
Summary Conclusions . . . . . . . . . . . 20
Part III Boise Area Water Quality: Managing Assimilative Capacity 22
A.
B.
c.
D.
Managing Water Quality: Water Use and the Effect on
Assimilative Capacity .
Current and Projected Loads on the Assimilative
Capacity of the Water Resource System . . .
Boise Area Water Quality Management System
Water Quality and Carrying Capacity: Summary
Conclusions . . . . . . . . .
Part IV Future Carrying Capacity Assessments: Issues
Part V Information Resources
vi
22
23
24
34
35
38
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List of Figures and Tables
Page
Figure 1 System Factors in Carrying Capacity Analysis . 3
Figure 2 Greater Boise Study Area . 5
Figure 3 Boise Area Water Resource System Model . 8
Figure 4A - 4B
Urban Water Consumption: Present and Future in Relation
to Estimated Carrying Capacity ............... 16-17
Table 1 Current Water Resource Demand, By Use Type, Quantities,
Qualities and Sources for the Boise Metropolitan Area . 12
Table 2 Comparison of Population Projections for Boise
Metropolitan Area . . . .
Table 3 Projected Water Resource Demand, By Use Type, Quantities,
Qualities and Sources for Boise Metropolitan Area:
. 15
1980 - 2000 . . . . . . . . . . . . . . . . . . . . . . . 19
Table 4 Major Water Pollutants and Their Effect on Water Quality . 24
Table 5 Water Quality Concerns in the Boise Metropolitan Area . 28
Table 6 Wastewater Facilities Construction Funding Sources . 31
Table 7 Sewer User Cost Impacts . 32
vii
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Part I Introduction To Carrying Capacity
A. Concept
The idea of carrying capacity was developed first by ecologists
to calculate the wildlife populations that could be sustained indef­initely
by the resources in a given area. The concept has been used
more recently in urban studies to estimate the relative populations and
activities that can be maintained within the constraints imposed by natural
resource limitations. Its earliest applications in management of
urban systems date from the late 1960's and early 1970's. There
still is no general agreement among theorists on the exact meaning
of the concept or the most effective methods of its application to
real communities.
Nevertheless, the concept of carrying capacity can be significant
for it requires citizens to study in an explicit manner the relation­ship
between people and their activities and environment and to develop
management policies and strategies for maintaining a harmonious and
supportive balance among these elements.
A. B. Bishop of Utah State University, a leader in this work,
defines carrying capacity as an estimate of the "level of human
activity, including population dynamics and economic activity, which
a region can sustain, including . . . . import and export of resources
and waste residuals, at acceptable 'quality-of-life' levels in
perpetuity." (#11, p. 32)
This definition suggests three elements or systems which must
be considered in carrying capacity studies. These are:
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(1) environmental systems -- air and watersheds,
land and plant and animal life;
(2) human activities -- the patterns of perceptions,
preferences and activities that make up the
human cultural, social, economic and political
systems; and
(3) the 11quality of life 11
-- a general term for the
well-being of people and the planet they inhabit.
The many complex relationships among these three factors mean that
carrying capacity is a complex, changing estimate rather than
a single, fixed number established as a population carrying
capacity. A number of environmental and human factors operate to
shape the carrying capacity of a region.
Bishop states:
11Attention, therefore, is directed toward viewing the
regional environment as a support system for numerous,
independent and frequently competing activities and
subsystems, where the determination of carrying capacity
rests upon desired human and environmental quality levels
which are circumscribed by a wide variety of political/
institutional, physical/biological, and social/cultural
constraints.
From this . . . . it should be clear that a human oriented
carrying capacity cannot be developed in a simple, single
numerical measure. It is not only a multidimensional con­cept,
but it is subject to constant change and modification
particularly as technological improvements are made and as
rules change due to pressures from the region 1 s residents.
From this perspective, carrying capacity must be inter­preted
~ ~ variable which is essentially socially deter­mined
within ~understanding of economic, social and
environmental values and their relative contribution in
maintaining quality-of-life levels. 11 (#11, pp. 30-33)
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-3-
The following diagram illustrates the relationship among these
elements.
Figure 1
System Factors in Carrying Capacity Analysis
ENVIRONMENTAL SYSTEM
a) Resources
1. fixed
2. renewable
b) Assimilative
capacity
QUALITY OF LIFE
a) Environmental
b) Human
B. Application
HUMAN SYSTEMS
cultural, social, political and economic
a) Reality descriptions - what 11 is11
b) Reality prescriptions - what 11 ought11 to be
c) Technological process - extraction,
production, distribution and disposal,
services and goods (tangible and intangible)
There is no single, agreed upon method for applying this concept
to studies of actual regions. However, a simplified approach, adapted
from H. Mogi, consists of six basic steps:
1. Identification of critical systems air, water, energy,
transportation, etc.;
2. Identification of geographic areas of critical systems;
3. Determination of limits of critical systems -- the resource
availability;
4. Determination of current and future resource utilization rates;
5. Determination of the margins, if any, for growth;
6. Identification of options and compromises involved in managing
the margins for growth. (#45, pp. 4-7)
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The present study will include the first f~ur steps and then
estimate future rates of population growth, resource demand and the
potential impacts for the study area. (See Figure 2} The emphasis
here is on assessing the current and potential future status of the
Boise urban system and the implications of such developments from a
carrying capacity perspective from the present to the year 2000.
In the course of the study, it is important to identify briefly
11 thresholds 11 or levels of effects which may be irreversible and may
alter carrying capacity or its utilization in fundamental ways, and
11 triggers 11 which are single events or a complex of events which push an
area•s carrying capacity or its utilization toward significant thresholds.
Finally, it is desirable for the purpose of the study, to identify
relationships between people and their environment so that citizens can
develop a personal connection to the complex issues of environmental and
human systems management. To this end, the study will suggest, where
appropriate and possible, the per capita demand on resource systems and
the per capita costs -- environmental and fiscal -- associated with
satisfying that demand.
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Figure 2
GREATER BOISE STUDY AREA
23.0l
West Bench.
Planning Ar
22.01
Southv1est
22.02
Source: (#67)
-5-
7
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Part II Boise Water Resources: Supply and Demand
Introduction -- For the purpose of this study, the critical system
of focus is the water resource base for the greater Boise area from
the present to the year 2000. The geographic area is defined more
specifically as the Boise metropolitan area within Ada County. {See
Figure 2) While that area is the primary focus of the study, it is
acknowledged that it is part of a larger watershed system; therefore,
where appropriate, the study will examine upstream factors which can
affect the study area, as well as those downstream impacts resulting
from activities within the primary study area. In general, Ada County
is the secondary emphasis of the study.
In examining water resources as a base for local carrying
capacity, it is useful to identify at least two related aspects of
water as a resource. The first is water as a support system for a
variety of intended uses involving various levels of necessary or
preferred water qualities. The other is the assimilative capacity
of water resources, or their ability to receive degradable and non-degradable
wastes or residuals without environmental degradation.
Water resources vary in this ability and their support capabilities are
modified by assimilative capacity. These distinctions are maintained
in the following report and serve to focus attention on estimates of
water demand and supply, quantities and qualities and the relations
between these twin elements.
A. The Water Resource System
Boise area water resources are the result of a complex set of
relationships between local climate, geography and geology. Together
these factors affect rates and amounts of precipitation, evaporation
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-7-
and flows within the Boise River drainage and the underlying shallow
and deep aquifer systems. Water resource availability is further
affected by modifications for water storage in upstream reservoirs
and canal systems which provide flood control and irrigation,
respectively, in Ada and Canyon Counties. These canals and reservoirs
indirectly support the aquifer system through groundwater seepage. A
brief outline of the hydrologic cycle will better serve to illustrate
these relationships.
1. Precipitation, either as rain or snow.
2. Evaporation/transpiration (water use by plants}.
3. Surface flows from and along the Boise River.
4. Reservoir storage for subsequent irrigation and recreational
uses.
5. Discharge through the river system.
6. Recharge of the groundwater aquifer by various surface water
sources.
7. The aquifer system consists of both shallow and deep aquifers
which are interrelated. Pumpage from the shallow aquifer
provides some residential and agricultural irrigation supplies.
The deep aquifer is the source of almost all water consumed
for residential, commercial and industrial purposes in the
Boise area. (See Figure 3)
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Figure 3
BOISE AREA WATER RESOURCE SYSTEM MODEL
6
6
-8-
b
6
6
~ PRECIPITATIONf
/j
tEVAPORATION/TRANSPIRATIONt
b
6
b
6
jl ! 1 1 ! 1:1' I! I! 1
1
1\j
RESERVO I R--)o.EO I SE RIVER DRAINAGE SYSTEM--.. CANALS-· .. I RR I GAT I ON--)o.DRAI NAGE--.. RUN OFF
J SEEPAGE l 1 1 1
DEEP AQUIFER
Graphic: Ann Dazey
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-9-
The Boise area water resource may be described as consisting of two
interrelated systems; a surface water system and a ground water (or aquifer)
system:
a) Surface water supplies
The principal surface water supply in the study area is the Boise
River which drains approximately 2,700 square miles of terrain lying to
the north and east of Ada County. The Boise River system has been
extensively modified by the construction of three major dams (Anderson
Ranch, Arrowrock, and Lucky Peak) located upstream from the city of Boise.
These dams provide reservoir storage for flood control, irrigation,
hydroelectric power production, and serve as a major source of water­based
recreation for residents of Ada County (#53, p. 18). Together
with Lake Lowell, this reservoir system contains approximately
1,157,000 acre-feet of active water storage capacity and provides
approximately 20,530 acres of water surface area (#53, p. 18). (Each
acre-foot of water contains 325,850 gallons.)
Five miles upstream from the city of Boise, the Boise River
Diversion Dam provides an average annual diversion of some
900,000 acre-feet of water into the New York Canal. This water
is then delivered to irrigated croplands throughout Ada and
Canyon counties through a system of latterals and canals or is
stored at Lake Lowell Reservoir in Canyon County for later irriga­tion
use. More than one-half of all irrigation water applied to
crops is not consumed and eventually returns to the river or
recharges the aquifer system (#59, p. 188).
There are a number of intermittent creeks or streams in the
area which contribute to the Boise River. They include Stuart
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-10-
Gulch, Crane Gulch, Hulls Gulch, Cottonwood Creek and Warm Springs
Creek.
b) Groundwater supplies
The groundwater or 11 aquifer11 system is composed of two
separate, but interdependent, aquifers -- one deep and one
shallow. The deep aquifer is generally located at depths greater
than 300 feet. The major zones of recharge to the deep aquifer
are the Boise Front, the bed of the Boise River above Boise, and
unlined portions of major irrigation canals (most significantly the
New York Canal). Discharge from the aquifer occurs through its
use as a supply source by the city of Boise and its natural dis­charge
to the Snake River (#20, p. 33).
The shallow aquifer is a much more dispersed body of water
which occurs primarily as a result of the over-application of
irrigation water. Discharge occurs through pumpage for domestic
use, pumpage for land drainage, and natural discharges through
seeps and springs. The shallow aquifer eventually drains into
the Boise River (#20, p. 36). Studies suggest that there is
some infiltration of water from the shallow aquifer to the deep
(#20, p. 33; #43, p. 11). The extent or effect of this infil­tration
is presently not known. The primary concern in this area
is the quality of the water found in the shallow system and the
degree to which it is a potential health hazard. This aspect of
the water resource will be discussed later in this report.
Perhaps the most important aspect of the carrying capacity
of an area•s water resource is the ability of that resource to
support an ever increasing population. In Boise, virtually all of
the water used for domestic purposes is drawn from the ground
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-11-
water system. The carrying capacity of the aquifer system can
be estimated conservatively as the rate of recharge that occurs
on an annual basis. Studies of the aquifer indicate that the
recharge rate for the study area alone is approximately 76,000
acre feet annually or approximately 24.7 billion gallons per
year (#75}. Note that this figure is very conservative since
the water available in the aquifer system is much greater than the
portion of the aquifer represented by the study area. Readers
interested in a descriptive account of the complexities of Boise
area hydrology are referred to works in Section V (see especially:
#20 and #43).
B. Present Water Resource Demand
The demand for or consumption of water resources by citizens of the
study area may be classed in the following use categories: 1} environ­mental
support for natural wildlife systems; 2) aesthetic enjoyment;
3} recreation; 4} domestic and agricultural irrigation; and 5} urban
consumption, which consists of residential, commercial, industrial; and
6} energy development (e.g., hydropower and geothermal).
The current types of use, levels of demand, the water qualities
entailed, and the primary sources within the water resource system
are indicated in Table l. The water resource demand presented here
includes demand by Boise area residents on water resources outside the
primary study area, but within the secondary area of the Ada County.
Note that the demand figures range from rather precise to very general
estimates, and that detailed measures are not readily available for some
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Water Use Type
TABLE 1
Current Water Resource Demand, By Use Type,
Quantities, Qualities and Sources for Boise Metropolitan Area
Estimated Quantities Required
Qualities Required by
State Regulations
1. Environmental Support 17.6 Billion Gallons of
Storage (provides 150 csf,
October through March)
Protected for:*
Cold Water Biota
Trout Spawning
2. Aesthetic
3. Recreational**
a) Fishing
b) Swimming
c) Boating
4. Irrigation
5. Urban Consumption,
Which Includes:
a) Residential
b) Commercial
c) Industrial
6. Energy Development
a) Geothermal
b) Hydropower
Not Calculable
Quantities Demanded.
Currently Creates
Congestion in Use of
Available Supply
3.26 to 4.89 Billion
Gallons/Year (study
area)
9 Billion Gallons/Year
Geothermal Development
Currently Requires 2000 to
4000 Gallons/Minute.
Hydropower Generation
Incidental to Release of
Water for Other Uses.
General Use
All Recreational
Uses
Agricultural Use
Domestic Use
Not Calculable
* See: Idaho Water Quality Standards; Re: Designated Beneficial Uses.
Sources of Supply
Boise River
Reservoirs, Boise River
Reservoirs, Boise River
Reservoirs for Storage and
Diversion of Boise River
Through Irrigation Laterals
and Canals
Groundwater System
Reservoir Storage for
Controlled Release and
Geothermal Groundwater
** Includes demand on water resource generated by citizens of Boise Metropolitan Area, on water resources
outside the primary study area, but within Ada County.
Sources: (#14, #23, #53, #71, #73, #75, #78, #84)
..I. ..
N
I
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-13-
of the uses under consideration. Their inclusion is necessary for any
comprehensive understanding of general carrying capacity; future research
efforts can clarify and provide more accurate assessments as these become
essential for decision-making.
Water quality requirements vary according to the intended uses of the
water and standards are established where necessary by the Idaho Department
of Health and Welfare Board. Water quality standards are set to preserve
or attain specified levels of quality; the relationship between most water
uses and quality is relatively well known and standards are established
accordingly. Some of the most stringent requirements are set for
environmental integrity since that relationship in some cases is well
known and policy-makers tend to create standards that are deemed likely
to be effective in protecting -- proven or presumed -- delicate natural
balances. Standards for water that is to be used in residential
consumption are set within criteria designed to protect or enhance human
well-being. Accordingly, there may be pre-treatment of domestic water
supplies. Boise Water Corporation currently treats water prior to
domestic use by the addition of chlorine for disinfection.
Data supplied by Boise Water Corporation permit a rough calculation
of per capita demands for water for urban consumption purposes in the
Boise metropolitan area. The current figure is approximately 170 gallons
per day, per person which includes residential, commercial and industrial
uses. The conventional rule of thumb nationally for water-supply
planning is 150 gallons per person, per day, which assumes a consumption
rate of 100 gallons for residential uses and increases that rate by
another SO% to reflect commercial and light industrial demand
(#46, p. 34). This comparison suggests that demand for domestic water
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-14-
resources in the Boise area is somewhat above the national level.
This information is useful as a water supply planning tool for it can
serve as the basis for assumptions about further water demand and supply
system requirements.
Boise Water Corporation data show that their average residential
customer pays approximately $155.00 annually for domestic water (#74).
Conversion of this annual figure to a per capita measurement shows
that water costs are approximately $.16 per capita per day. The Boise
Water Corporation has applied to the Idaho Public Utilities Commission
for permission to increase its water rates by 17.9 percent, due primarily
to increased energy costs, which account for nearly 24 percent of the
firm•s total operating costs. The status of the proposed rate increase
is unknown at this time.
C. Projected Water Resource Demand
Estimates of future demand for area water resources depend essentially
on assumptions about population growth and patterns of water consumption
behavior. The population projections most widely used locally are from
the Ada Planning Association (1978) and the Idaho Population and Employment
Forecast (1978). These are reprinted in Table 2.
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APA (1978)
IPEF* (1978)
-15-
Table 2
Comparison of Population Projections
for Boise Metropolitan Area
1985 1990 1995 2000
*The IPEF estimates population by counties only. Historically, 87 percent of
Ada County•s population lived within the Boise metropolitan area. To coincide
with many of the studies used to prepare this report, it is assumed that this
relationship still exists. These figures are derived accordingly.
Boise Water Corporation records have shown that as incomes have risen in
the area, the per capita use of water has also risen by a small percentage.
The company bases its future projections of urban water use on the assumption
that this trend will continue; it estimates that by the year 2,000 the per
capita consumption rate will be 204 gallons per day. Other local experts,
however, believe that the per capita consumption will remain near the present
figure of 170 gallons per day through the year 2,000.
It is possible to construct utilization curves which project the total
annual urban water consumption rate in relation to estimated carrying capacity
according to three alternative per capita, per day use rates. Each is used to
represent different patterns of use due to the price of water or the level of
conservation employed by water users. The ranges are: 1) Low, 150 gallons
per day; high cost, high conservation, 2) Medium, 170 gallons per day;
moderate cost, moderate conservation; 3) High, 200 gallons per day; low cost,
low efforts to conserve. These estimates appear in Figure 4A and B.
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26
-16-
Figure 4A
URBAN WATER CONSUMPTION: PRESENT AND
FUTURE IN RELATION TO ESTIMATED CARRYING CAPACITY
(USING APA POPULATION PROJECTIONS)
HIGH CONSUMP110N MEDIUM CONSUMP110N LOW CONSUMP110N
200 GPO PER CAPITA 170 GPO PER CAPITA 150 GPO PER CAPITA
-~· ... 0· .
ANNUAL CONSUMP110N-BIWONS OF GAI.l.ONS
I I I
24
···~······························································································
\ CARRYING CAPACITY ESTIMATED AS ANNUAL
RECHARGE RATE FOR THE STUDY AREA
22
20
18
~
16
14 / -------· ----·-- . _....-- --· .... .;~--
12
~ --· .. --· .. . .
"" .. ·- -· .......... - ·t'".:,. •.•
10
8
1980
I
1985
I
1990
...._.--· --· --·
__ .. ,.. ... --·. .
CARRYING CAPACilY STUDY PERIOD-YEARS
NOTE: Current consumption rate = 170 gpd per capita.
_..
. .._ £:>.
l
1995
~
-·
___ ... --·-- ..... w. , . .
.~·. .- -- . --
2000
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26
-17-
Figure 4B
URBAN WATER CONSUMPTION: PRESENT AND
FUTURE IN RELATION TO ESTIMATED CARRYING CAPACITY
(USING IPEF POPULATION PROJECTIONS)
HIGH CONSUMPTION MEDIUM CONSUMPTION LOW CONSUMPTION
200 GPO PER CAPITA 170 GPO PER CAPITA 150 GPO PER CAPITA
-~· ·•.
ANNUAL CONSUMPTION-BilliONS OF GAU..ONS
I I I
24
···~······························································································
'\CARRYING CAPACITY ESTIMATED AS ANNUAL
RECHARGE RATE FOR THE STUDY AREA
22
20
18 /
/
~
.. /
./
./
...._./
16
14
~ ~ --· --· --·- --· _.A--· .. .. ·.:·
12
10
~:~:~---·
8
1980
~ ~- '{'::~ ,. ...
I
1985
.•..
I
1990
--· --· --·
"'.
CAARYING CAPACITY STUDY PERIOD-YEARS
NOTE: Current consumption rate = 170 gpd per capita.
_... ......
I
1995 2000
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-18-
Future demand of water resources for purposes other than urban consump­tion
are estimated in a general way; no detailed projections are available
for this report. It is suggested that local area demand for waterbased
outdoor recreation -- fishing, swimming and boating -- will nearly double
by the year 2,000 (#23, p. 91). Thus, the assumption appears reasonable
that demand for environment support, aesthetic and recreational uses of
water by Boise area residents will increase faster than population growth.
This level of demand will focus on water resources and their quality within
the primary study area, especially the Boise River and Greenbelt environs,
as well as water resources with the secondary study area of Ada County.
Decline in the number of irrigated farm acres within the study area,
and the county generally, will reduce the demand for surface water sources
for agricultural irrigation.
It is also possible that the next two decades will see increased
competition among various users for opportunities to use the surface
waters within the primary or secondary area of this study. Increased use
of surface waters -- especially Lucky Peak Reservoir and the Boise River
may be compatible, rather than competitive, in some instances. In most
cases, however, the uses will not be compatible. Increased consumer
dissatisfaction with quality of life levels or increases in participation
costs due to pollution or congestion and maintenance of water quality
standards may reduce general satisfaction with area water resources.
These possibilities are not estimated currently, but future study
could lead to more accurate projections.
Future estimates of demand on water resources, by use type, quantity,
quality and source are summarized in Table 3. Assumptions that water quality
requirements will remain at present levels, if not higher, are based on
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TABLE 3
Projected Water Resource Demand, By Use Type,
Quantities, Qualities and Sources for Boise Metropolitan Area
Water Use Type
Quantities Required
Estimated
1. Environmental Support 17.6 Billion Gallons of
Storage {provides 150 cfs,
October through March}
2. Aesthetic Not Calculable
3. Recreation** Demand Expected to Double
a) Fishing
b} Swimming
c) Boating
4. Irrigation Demand Expected to
Decrease Within Study
Area
Qualities Required
Estimated*
Continued Protection
for Cold Water Biota
Trout Spawning
General Use
All Recreational
Uses
Agricultural Use
5. Urban Consumption
a} Residential
12 to 16 Billion Gallons/Year Domestic Uses
b) Commercial
c) Industrial
6. Energy Development
a} Geothermal
b} Hydropower
by 2000.
a) Future Geothermal Development Not Calculable
Requirements Depend Upon the
Performance of the System.
Currently Under Construction.
b) Hydropower Generation in the
Future will be Incidental to
Release of Water for Other Uses.
* See: Idaho Water Quality Standards; Re: Designated Beneficial Uses.
Sources of Supply
Boise River
Reservoirs, Boise River
Reservoirs, Boise River
Reservoir Storage, Diversion
of Boise River
Groundwater System
Reservoir Storage.
Geothermal Groundwater.
** Includes water resource generated by citizens of Boise Metropolitan Area, on water resources outside the
primary study area, but within Ada County.
Sources: (#14, #23, #53, #71, #73, #75, #78, #84)
I
1-'
\D
I
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-20-
national polls indicating that approximately 94% of the American people
favor retaining the Clean Water Act. The likely local increase in water­based
recreation will also tend to favor present or, perhaps, more stringent
quality standards.
It is necessary here to consider briefly the carrying capacity of the
system which provides and allocates our water resources. The elements of
that system include private organizations and public agencies responsible
for providing or maintaining the quantities of water resources, at required
qualities, that serve residents within greater Boise and Ada County.
In general, there are no detailed estimates of carrying capacities
made available by such agencies. Facilities projections done by Boise
Water Corporation indicate no general problem, technical or financial,
with providing quantities and qualities of water that may be required
during the study period. Spot difficulties with pumpage, leakage,
distribution, pressure or quality may occur infrequently but are expected
to be manageable. Costs will increase due to rising prices for electrical
energy; detailed cost projections are not available for this study. Further
studies into these aspects of carrying capacity may be warranted for all
water use types and the providers within the study area.
D. Water Resource Supply and Carrying Capacity: Summary Conclusions
From the carrying capacity methodology developed herein and estimates
of water supply and projections of current to future water demand, it is
possible to derive the following summary conclusions:
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-21-
1. Estimated water supplies for urban consumption -- residential,
commercial and industrial uses -- under alternative consumption
rates and growth scenarios are more than adequate to meet
demand during the next two decades.
2. Estimated water supplies for agricultural irrigation within the
study area are adequate through the year 2000. Demand for irrigation
will decline during this time due to growing urbanization in the
study area.
3. Demand on water resources for environmental aesthetic and recreational
purposes will increase due to population growth and high participation
rates:
4.
a. Available supplies may produce reduced material, or
psychic satisfaction due to congestion, pollution or costs
associated with maintaining present water quality standards.
b. Competition among users for surface waters, especially in
summer months, will increase.
a. Estimates of the carrying capacity of municipal water
provision system indicate no anticipated problems with
providing required quantities to consumers. Costs will be
higher.
b. Temporary and spot difficulties in pumpage, leakage,
pressure and quality are anticipated, but are considered
manageable by local water experts.
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-22-
Part III. Boise Area Water Quality: Managing Assimilative Capacity
A. Managing Water Quality: Water Use and the Effect on Assimilative
Capacity
The carrying capacity perspective on water quality is emphasized
in this statement from the Council on Environmental Quality:
11 Ideally, water quality would be measured in terms of its
impacts on all living systems, human and other. But
because measuring the functions of biological systems is
difficult, water quality is described by the extent to
which lakes, rivers and streams can physically, biologically
and chemically support aquatic life and meet the standards
recommended for human use.
Efforts to keep water clean or to restore it to a healthy
state center on controlling the amount and kinds of materials
that are dumped or washed into waterways, the ground and
the air. Water quality or rivers, lakes and oceans depends
upon their individual capacity to handle a given pollutant.
In turn, the capacity varies with the type and amount of
the pollutant; water temperature, flow, sediment and mineral
content.
Under Federal law, the Government is directed to •restore
and maintain the chemical, physical and biological integrity
of the Nation•s waters• -- to eliminate the discharge of
pollutants by 1985; to maintain water quality that protects
fish, shellfish and wildlife, and provides for recreational
use by 1983, and to prohibit the discharge of toxic sub­stances
in amounts that are toxic to humans and wildlife.
(#56, p. 237)
This focuses attention on the critical importance of 11 assimilative
capacity, 11 or the ability of water resource systems to handle various
types and quantities of pollutants without degradation of the environ-mental
system. Assimilative capacity varies with circumstances, and
the knowledge of ecologists about complex environmental relationships
involving water resources is inexact and incomplete. Thus, estimates
of carrying capacity may vary widely, depending on the assumptions
made and the knowledge available. In many cases, experts differ on
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whether assimilative capacity is relatively limited and fragile, or
whether it is extensive and rather resilient.
Since assimilative capacity is affected by the type and amounts
of pollutants and their effects on human and other life systems, it
is useful to survey the major water pollutants and their effects
on water quality. Table 4 summarizes these relationships.
B. Current and Projected Loads on the Assimilative Capacity of
the Boise Area Water Resource System
Because assimilative capacity is an estimation based on best available
knowledge, it is appropriate to use water quality standards as proxy measures
of carrying capacity. These standards for the study area are set by the Idaho
Department of Health and Welfare Board. For the purpose of this study, the
standards themselves are not as important as are estimates about meeting or
violating these standards in the present or the future. Accordingly, readers
interested in a detailed listing of water quality standards are referred to
Idaho Water Quality Standards and Wastewater Treatment Requirements (#29).
Precise estimates of current water qualities in the study area and
whether carrying capacity is met or exceeded, and if so, with what frequency
and magnitude, are difficult to make due to measurement, monitoring and
reporting practices. Projections from current to future situations are even
more difficult given measurement and impact assessment capabilities and the
choice of assumptions that may be most appropriate over the next several
decades. Nevertheless, general estimates are possible, based on current
measurement practices and the informed judgment of experts involved in water
quality management.
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Type of waste
Disease-carrying agents-­human
feces. warm-blooded
anrrnal feces
Oxygen-demanding wastes-­high
concentrations of
biodegradable organic matter
Suspended organic and
inorganic matenal
Inorganic materials.
mineral substances-­metal.
salts. acids.
solid matter. other
chemicals. oil
Synthetic organic chemicals-­dissolved
organic material.
e.g., detergents. household
aids, pesticrdes
Nutrients--nitrogen,
phosphorus
Radioactive materials
Heat
Source:
Table 4
MAJOR WATER POLLUTANTS AND THEIR EFFECT ON WATER QUALITY
(NOT ALL APPLY TO THE BOISE STUDY AREA)
Wastewater sources
Munictpal discharges.
watercraft ::iischaroes. urban
runoff. agncultural~ runoff.
feedlot wastes. combinPd
sewer overflows. industnat
discharges
Municrpal discharges.
industnal discharges.
combined sewer overflows.
watercraft discharges.
urban runoff. agricultural
runoff. feedlot wastes.
natural sources
Mining discharges. municipal
discharges. rndustrial
discharges. construction
runoff. agricultural runoff.
urban runoff. silvicultural
runoff. natural sources.
combrned sewer overflows
Mining drscharges. acid mine
drainage industrial
drscharges. municipal
discharges. combined sewer
overflows. urban runoff. oil
fields. agncultural runoff.
irrrgation return flow. natural
sources. coolrng tower
blowdown. transportation
spills. coal gasification
Industrial discharges. urban
runoff. municipal discharges.
combined sewer overflow.
agricultural runoff. silvicullural
runoff. transportation spills.
minrng drscharges
Municipal discharges,
agricultural runoff. combined
sewer overflows. industrial
discharges. urban runoff.
natural sources
Industrial discharges.
mining
Cooling water drscharges.
industnal drscharges.
rnunrcrnal drscharges.
cootinq tower blowdown
(#56, p. 239)
Water quality
measures
Fecal coliform. fecal
streptococcus. other
microbes
Effects on
water quality
Health hazard for
human consumption and
contact
Biochemical oxygen demand, Deoxygenation. potential !or
drssolved oxygen. volatile septic conditions
soltds, sulfides
Suspended solids. turbidity, Reduced light penetration.
biochemical oxygen demand. deposition on bottom.
sulfides benthic deoxygenation
pH, acidity, alkalinity,
dissolved solids. chlorides.
sulfates. sodium, specific
metals. toxicity bioassay,
visual (oil spills)
Cyanides, phenols. toxicity
bioassay
Nitrogen. phosphorus
Radioactivity
Temperature
Acidity, satination. toxicity
of heavy metals. floi!ling oils
Toxicity of natural organics.
biodegradable or persistent
synthetic organrcs
Increased algal growth.
dissolved oxygen reduction
Increased radioactivity
Increased temper
I
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The most recent survey of Boise area water quality notes: 11 the
quality of Boise Valley water resources ranges from generally good
to excellent. Surface water from the Eastern Uplands is of highest
quality, shallow groundwater and agricultural drain waters have the
poorest quality, and deep groundwater is of relatively intermediate
quality. 11 (#59, p. 194) That report states further:
11The water quality conditions of the Boise River and
its tributaries have been extensively studied since
the early 1970 1s. Sampling has included dissolved and
suspended constituents, bacteria and the biotic com­munities.
Sampling agencies have included:
o Ada Planning Association
o U.S. Bureau of Reclamation
o City of Boise
o Boise State University
o Idaho Department of Health and Welfare
o U.S. Army Corps of Engineers
o Idaho Department of Fish and Game
o U.S. Environmental Protection Agency
o U.S. Fish and Wildlife Service
Water quality conditions are governed by various
point source discharges, by agricultural return flows
and by river flow available to dilute pollutant loads.
During the winter non-irrigation season, flow in the
river below Lucky Peak is often insufficient to provide
adequate dilution of wastes discharged in the river.
In the irrigation season, diversion of flow for agricul­tural
usage may create low flow conditions in the
vicinity of Star. Below Star, flows again increase
due to agricultural return flows.
Generally, the water quality of the Boise River
worsens downstream of Boise. This degradation is due to
the various point and nonpoint source pollutant loads
entering the river. Several industrial discharges, in
addition to the municipal waste load, add significant
pollutant loads. Agricultural drains also account for
a portion of the total pollutant load in the river.
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Temperature. The temperature of the Boise River in­creases
in downstream direction and is especially
elevated during the summer months. An increase in
water temperature occurs between Caldwell and Parma
stations, which have average summer temperatures of
14.9°C and 17.4°C, respectively. The flows in this
reach are governed by agricultural return flows.
Dissolved Oxygen. Adequate levels of dissolved
oxygen are necessary for the survival of fish and
other aquatic organisms. STORET (EPA computerized
data base) data show that dissolved oxygen concen­trations
in the Boise River decrease in a down­stream
direction during the summer months. During
the winter, the average dissolved oxygen is relatively
stable, with only a slight decrease downstream. The
agricultural drains usually have lower dissolved
oxygen concentrations than the Boise River.
Ada Council of Governments (ACOG 1975d) found dis­solved
oxygen concentrations to decrease in a down­stream
direction. The concentrations, however, were
determined to be within acceptable limits for the
beneficial uses along the river.
At Star, EPA (197la) found minimum percentage
dissolved oxygen saturation. Star is the point in
the river where flows are greatly reduced, often
approaching a no-flow condition.
Nutrients. The major nutrients used by algae and
other aquatic plants include various nitrogen and
phosphorus compounds. Nitrogen released in sewage
effluent is primarily in the form of organic
nitrogen or ammonia. Various bacteria decompose
the organic nitrogen to ammonia, while other bacteria
convert ammonia to nitrite and nitrate. Algae can
convert ammonia, nitrite or nitrate; the nitrate form,
however, is most readily used. While ammonia and
nitrite can serve as plant nutrients, these two
forms of nitrogen can also be toxic to fish.
Very little ammonia is found in the river above Boise.
Ammonia concentrations reach a maximum (0.43 mg/1 in
winter) at Glenwood Bridge. The increase is due to
wasteloads, especially treated municipal sewage,
entering at Boise. Below Boise, the river shows
improvement with the ammonia concentrations decreasing
downstream direction, with the highest concentrations
found at Parma. The large nitrate concentration
at Parma is due not only to upstream discharges of
ammonia, organic nitrogen and nitrite from waste­water
effluent, but also due to runoff from agri­cultural
lands.
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Total phosphate and orthophosphate increase in a down­stream
direction. Orthophosphate averages 0.01 mg/1
below Lucky Peak and 0.30 mg/1 at Star. The increase
is primarily in response to runoff from agricultural
acreage or accretions from groundwater recharge from
irrigation and treated sewage effluent.
Biochemical Oxygen Demand. Biochemical oxygen demand
(BOD} is an index of the oxygen-consuming organic sub­stances
in water. High BOD levels can deplete the
dissolved oxygen necessary for survival of sih and
other aquatic organisms. The BOD in the Boise River
does not show large increases over upstream concentra­tions
until the station at Parma. During summer
conditions, organic materials are readily oxidized.
Consequently, the effect of oxidizing BOD loads shows
up as lower oxygen concentrations rather than increased
BOD concentrations. In the winter, colder temperatures
inhibit the organisms that oxidize organiz material,
and BOD increases at the downstream stations."
(#59, pp. 194-200}
For more detailed discussion of current and future estimates
regarding pollutant loadings and water quality, the reader is
referred to the resource document cited, especially Chapters 10 and 11.
See Table 5 for a list of water quality concerns in the Boise Metropolitan
Area.
C. Boise Area Water Quality Management System
Water quality management focuses both on point (source} or non-point
(general source} pollution and the treatment of effluents,
both degradable and non-degradable. In general, pollutants from
point sources are treated prior to discharge, either to land or to
receiving bodies of water. Treatment involves methods of collecting,
filtering and cleansing -- using chemical, biological or mechanical
processes -- and then either concentration of toxic or non-degradable
effluents for later disposal or dilution of degradable effluents
for discharge within permissible limitations to receiving waters.
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Concern
1. Municipal Wastewater
Treatment Facilities
2. Individual On-Site
Sewage Disposal
Systems
3. Individual Industrial
Wastewater Generators
4. Urban Storm Runoff
5. Geothermal Effluents
Table 5
WATER QUALITY CONCERNS IN THE BOISE METROPOLITAN AREA
Pollution Parameter
Ammonia, Flouride
Chlorine, Heavy Metals
Biological Oxygen Demand (BOD)
Total Suspended Solids (TSS)
Bacteria
Nitrate
Coliform Bacteria
Heavy Metals
Heavy Metals, Oil-base
Pollutants, TSS
Flour ide
Thermal Pollution
Impact
Harmful to Aquatic
Life, Degradation of
Water Quality for Other
Uses
Adverse Health Affects
if Ingested
Harmful to Aquatic Life
Degradation of Water
Quality for Other Uses
As Above
As Above
Sources: (#4, #17, #59, #71, #82)
Water Source Affected
Boise River
Shallow Groundwater Aquifer
(possible adverse effects
to deep aquifer and Boise
River)
Boise River
Boise River
Boise River
I
N
00
I
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Non-point sources of pollution are primarily urban stormwater
runoff and other drainage waters and agricultural runoff and associated
sediments and chemical or biological pollutants. Nationally, non-point
sources typically account for over SO% of all pollutant loadings to
receiving waters and over 80% of all organic discharges after waste­water
treatment (#57, p. 133). While most areas, including the Boise
metropolitan region and Ada County, are aware of the necessity of
planning for and managing water quality regarding the non-point sources,
it remains difficult to achieve effective management in practice. The
Council on Environmental Quality notes that the "control of pollutants
discharged directly from industrial and municipal sources . . . into
waterways is progressing, but little progress has been made in the
kinds and amounts of materials that enter waterways from erosion,
urban runoff and many other general sources . 11 (#56, p. 237)
From a carrying capacity perspective, it would be most desirable
to know the current sources of non-point pollutants, types and
quantities and their impacts on the receiving water systems in the
Boise and Ada County area. While some studies exist (#21), they
are not comprehensive or detailed enough to provide the necessary
information. Local experts in water quality management agree that
urban stormwater is probably one of the most pressing issues in
water quality management in the study area, given the magnitude of
the problem, its impact and the inadequacy of present plans or
facilities to handle the situation and the financial costs of any
effective system for doing so (#2 #59, #66, #69, #71). Further studies
of the urban stormwater problem have been proposed, but funding is
currently unavailable.
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Much more is known about the nature of point (source) pollution
from industrial, commercial and residential uses of water and the
methods for managing water quality as a result. Management strategies
may be characterized as centralized wastewater collection, treatment
and disposal-discharge systems, or decentralized, on-site systems for
the treatment of wastewater.
In the primary study areas, this approach generally involves
centralized wastewater treatment facilities operated by the City
of Boise for the Boise and Garden City areas, smaller waste treat­ment
systems for several areas and septic tank systems for the
rural, non-sewered portions of the primary study area.
The City of Boise currently operates three wastewater treatment
plants: Lander Street, West Boise and Gowen Field. The Boise
Wastewater Facilities Plan (#17, Chapter II, pp. 12-13) describes the
loads and capacities as follows:
Lander Street: operating near capacity 1n terms of flow
and organic loads.
West Boise: currently overloaded during the summer months due
to large amounts of groundwater or stormwater (infiltration and
inflow, respectively) which leak into the sewer system.
Gowen Field: currently underloaded.
The study indicates further, that planned modifications and improve­ments
in the Boise wastewater treatment system, including pipelines and
interceptors, would increase capacity sufficiently to carry the loads
projected through the year 2000. These plans, however, are contingent
upon federal and state participation in the funding of wastewater facilities.
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Historically, the U.S. Environmental Protection Agency has provided
75% of the eligible capital costs for wastewater treatment facilities,
with the Idaho Department of Health and Welfare granting an additional
15%. The local entity was then required to provide only 10% of the
eligible costs. The State of Idaho has determined that total grant
assistance shall not exceed 75% of the total cost of the facility.
This raises the local share of construction costs to 25%. By October 1,
1984 (fiscal year 1985), the federal grant portion will drop to 55%,
obligating the local entity to provide 45% of construction costs.
These data are summarized in Table 6.
Funding Source
EPA
IDHW
Local Funds
Table 6
WASTEWATER FACILITIES CONSTRUCTION
FUNDING SOURCES
Historical Present to 9-30-84
75% 75%
15 0
10 25
100% 100%
After 10-1-84
55%
0*
45
100%
*The State has not yet determined if it will participate to bring the total
grant up to 75%, and thus decrease the local share from 45% to 25%.
Sources: (#17, #66)
As government at all levels currently trim their budgets, many projects
which are legally eligible under the laws and regulations are practically
eliminated from consideration by the lack of sufficient money to fund all
eligible projects. Therefore, a priority system has been established.
Projects which are not high on the priority list will require 100% local
funding without state or federal assistance. Consequently, the local
share of some projects, rather then increase from 10% to 25% to 45%
(Table 6), will actually increase from 10% to 100% local
funding as a result of declining governmental support.
Beginning October 1, 1984, the federal government will provide
wastewater facilities construction grants only for the purpose of providing
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for present needs. If local facilities are expanded to anticipate growth,
the funding will have to be obtained locally. This approach suggests
that in order to be eligible for federal grants, the facility must be
over capacity. Formerly, a wastewater treatment facility was designed
to provide for 20 years of projected need.
The City of Boise uses two methods to generate needed revenue. One
method is user charge, which is monthly fee to each user based on non-irrigation
water consumption. This fee is used to pay all operating costs
and to help fund plant replacement. The second method is a connection
fee which is a one-time charge paid when a new horne or business connects
to the system. This fee is used to finance facility expansion. As the
local share of such expansion begins to grow, it is anticipated that an
upward pressure on both fees can be expected. See Table 7.
1980 Average
Present Average
Table 7
SEWER USER COST IMPACTS
User Charge
$0.10/capita/day
(2.86/capita/rnonth)
$0.11/capita/day
(3.19/capita/rnonth)
Connection Fee
$165.00
$360.00*
*This connection fee was increased as a result of the State's decision to
drop their 15% participation. It does not reflect any decrease in Federal
participation. Boise Public Works officials state that a connection fee
increase to approximately $800 is justifiable given current policies but
is felt to be unacceptable at this time.
Sources: #17, #69
Non-sewered portions of the study area are serviced by community-type
or on-site wastewater treatment systems. Because these systems dispose of
wastes beneath the ground, there has been concern expressed for the protec-tion
of water quality within the aquifer. Recent studies of Southwest
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Boise have documented an upward trend in nitrate concentrations in local
wells, which suggests the potential for future groundwater contamination
(#4, Sec III, pp. 2-4, #6, #59, p. 178).
On August 1, 1980, the Ada County Commissioners adopted the Southwest
Community Comprehensive Plan which limited new development in the area to
a maximum density of one dwelling unit per five acres. This plan acknow­ledged
the potential for groundwater contamination but chose to limit
population density rather than to incur the costs of extending central
sewer service from Boise or providing new central treatment facilities
for the area. The feeling of most area experts is that the adoption of
this land-use plan has essentially closed off the possibility of providing
centralized sewer service to Southwest Boise in the near future.
In the opinion of area water quality experts, the Boise River is at
its capacity to assimilate certain pollutants. These pollutants are
ammonia, flouride and some heavy metals. The loading from the various
point and non-point sources of pollution combined with the extreme
variability in river flow has placed a great deal of pressure on the
river 1 s carrying capacity, according to the current water quality standards.
In winter months, the river 1s carrying capacity is greatly diminished
by the extreme low-flow conditions which limit its capacity to assimilate
pollutant loads. The Idaho Water Quality Standards are designed to protect
the designated uses of the river under these low-flow conditions. During
the irrigation season, there is ample flow which allows the river to
assimilate loading, but under low-flow conditions, the Boise wastewater
treatment plants are required to increase their level of treatment to
protect water quality. This increased treatment raises the costs of
treatment by approximately 5% on an annual basis (#69).
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If the Boise River is at capacity, the community faces three
basic alternatives:
1. Decrease the water quality standards and thus increase
the river's "defined" carrying capacity. This alternative
has the potential to degrade the water for the designated
uses and may adversely affect the quality of life of citizens
in and around the study area. Further, this alternative would
be subject to review by the Environmental Protection Agency,
which has the authority to refuse such an action and to set
standards that it deems appropriate and necessary to protect
or enhance water quality.
2. Increase levels of treatment for those who discharge wastewater.
This alternative would increase costs of treatment and thus raise
costs to users of the system.
3. Increase the flow of water in the Boise River during the low-flow,
winter months. There is at present approximately 116,000 acre
feet of unallocated storage space at Lucky Peak Reservoir. This
space could be filled and partially used to augment river flow and
thus increase the carrying capacity of the river. This alternative
is under investigation by the Bureau of Reclamation (#70}.
D. Water Quality and Carrying Capacity: Summary Conclusions
1. In the opinion of area water quality experts, the Boise River
is at carrying capacity for certain pollutants according to
present water quality standards. Possible alternatives include:
a. Decrease the present water quality standards.
b. Increase levels of wastewater treatment.
c. Increase Boise River flows.
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2. The capacity of the Boise wastewater treatment plants is as
follows:
Lander Street: at capacity. No plans to expand the current
facility. Excess loads are to be diverted to the West Boise Plant.
West Boise: at capacity, due to present unit process limitations.
This facility is planned to accept the major loads expected from
future population increases. The funding for upgrading or expand­ing
this facility is expected but has not yet been formally awarded.
Gowen Field: under capacity at this time. This plant disposes
of treated wastewater on land areas and is not a threat to water
quality at this time. Further, this plant treats a very small
percentage of the area sewage and is not designed to accept major
increases in load.
3. The federal government has adopted policies which will reduce
its share of local wastewater treatment facilities construction
and expansion costs. Further, after October 1, 1984, the federal
government will no longer fund the expansion of facilities to
meet future needs. These steps greatly increase the costs of
facilities that must be borne locally and will raise costs
for users of centralized sewer systems to better reflect the
actual costs of building and maintaining such facilities.
Part IV. Future Carrying Capacity Assessments: Issues
A. Assumptions and Trends
As noted earlier, carrying capacity assessment is an on-going process
that leads to changing estimates of resource supply, demand and costs -­environmental
and financial. Therefore, this section briefly examines
some of the issues arising for future carrying capacity studies or updates
of the present study.
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The first issue concerns whether or not present estimates of water
resource supplies are accurate and if projections of population growth
and consumption behavior are accurate. Events not now foreseen or
anticipated could trigger substantially altered population growth rates
or changes in consumer demand for all types of water uses.
These possibilities need to be recognized, and as early signals
of such occurrences are available, these may be used to revise carrying
capacity analysis. Similarly, as new information becomes available
on recent trends, these assumptions may be altered accordingly, and
will affect future such assessments.
B. Research Needs
The foregoing analysis has noted in numerous instances where
comprehensive, complete and accurate information necessary for a
thorough carrying capacity assessment is not available. This may stem
from gaps in our theoretical understanding of complex relationships
among environmental and human systems. Other lacks may arise from gaps
in our applied knowledge of specific situations within the study area.
An additional possibility is that much available information -- theoretical
and applied -- is not collected, assembled and reported in a manner that
makes it easily available for or applicable to carrying capacity assessments.
More information on the following issues would be especially
helpful to citizens and policy-makers in the study area:
Updated population projections as 1980 census data become
available.
-- Expanded investigation of non-point sources of pollution to
determine the extent of their contribution to total pollution loads and
to develop management alternatives with which to control these sources
of pollution.
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-- Continued groundwater well monitoring, particularly in Southwest
Boise, to assess potential health hazards in domestic water supplies.
-- An assessment of the impact of declining federal assistance for
wastewater treatment plant construction and expansion and the extent to
which local sewer charges will increase as a result.
-- Survey and evaluate funding alternatives -- federal, state and
local -- for improvement and expansion of Boise area waste treatment
facilities and the per capita control costs for increments of improvement.
-- Survey the extent to which water quality is a component of the
"quality of life" for Boise area residents.
Carrying capacity studies focus attention on relationships between
people and their environment in ways generally not found in previous
studies. If policy-makers and citizens find the carrying capacity
perspective a useful one, it will become necessary to focus further
research efforts on obtaining the required information. Effective and
efficient methods of acquiring and maintaining it readily available
for guidance in community decision-making can be developed and managed
successfully. That information can assist the community in making
decisions based on greater awareness of the relationship between
environmental resources and human activities and the effects on the
area•s quality of life.
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Part V. Informational Resources
A. Printed Documents
1. Ada/Canyon Waste Treatment Management Committee. 1978.
Individual Waste Disposal Systems Management Plan. Ada
and Canyon Counties, Idaho.
2. Ada/Canyon Waste Treatment Management Committee. 1978.
Areawide Water Quality Management Plan for Ada and Canyon
Counties, Idaho.
3. Ada/Canyon Waste Treatment Management Committee. 1977.
Municipal Waste Treatment Plan. Ada and Canyon Counties,
Idaho.
4. Ada Planning Association. 1981. Ada County Domestic Wastewater
Management Plan. Boise, Idah~
5. Ada Planning Association. 1981. Southwest Community Wastewater
Management Plan. Boise, Idaho.
6. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study; Groundwater Report, Technical Memoranda 308.04g.
Boise, Idaho.
7. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study: Inventory and Evaluation of Public and
Private Central and Community Collection and Treatment
Systems. Technical Memoranda 308.04j. Boise, Idaho.
8. Ada Planning Association. 1979. Southwest Community Wastewater
Management Study: Preliminary Alternatives -- Description
and Evaluation. Technical Memoranda 306.04j. Boise, Idaho.
9. Ada Planning Association. 1978. Demographic and Employment
Distribution to the year 2000. Boise, Idaho. 198 pp.
10. Berry, Brian and Frank E. Horton. 1974. Urban Environmental
Management. Prentice-Hall, Inc. Englewood Cliffs,
New Jersey.
11. Bishop, A. B. 1974. Carrying Capacity in Regional Environmental
Management. Utah State University. Logan, Utah. Prepared
for EPA.
12. Boise City. Metro Plan. Boise, Idaho.
13. Boise Project Board of Control. 1981. Annual Report. Boise,
Idaho.
14. Boise Water Corporation. 1980. Projection Study for Boise Water
Corporation. Boise, Idaho.
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15. Carey, George W. 1972. Urbanization, Water Pollution, and Public
Policy. Center for Urban Policy Research, Rutgers University.
16. Central District Health Department. 1979. Southwest Boise Water
Study. Boise, Idaho.
17. CH2M Hill, Inc. 1980. Boise Wastewater Facilities Plan: Summary.
18.
19.
Prepared for the City of Boise. Boise, Idaho.
CH2M Hill, Inc. 1980. Wastewater Facilities Plan, Boise, Idaho,
Parts I and II. Boise, Idaho.
Ehrlich, Paul R.
Environment.
California.
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